See Volvagia for the boss fight in Fire Temple.
In rooms where a heat timer pops up if Link isn't wearing the Goron Tunic, the amount of time on the timer corresponds to Link's health when the room loads, with 1 second on the timer for each 8th of a heart. However, the game keeps track of Link's health in 16ths (see glitched health for more information), so if Link has exactly 1/16 of a heart, the heat timer will fail to pop up at all. This is useful for speedruns that skip the Goron Tunic but still need to spend time in heat timer rooms, such as Volvagia's.
Getting Link down to 1/16h can be tricky because the HUD only displays hearts in quarters. When Link is on fire, he takes 1/16h of damage every 8 frames until he's extinguished, which happens on its own after 1.25h have been dealt (on top of the initial hit). The 10 frame cycle of the hearts pulsing on the HUD can be used to time using the sword or running to extinguish the flames during the 8 frame window where Link has 1/16h but isn't yet dead, as shown in the video below. Note that flames aren't extinguished by walking slowly or crouching with shield.
There is also a longer tutorial with visual aids linked here.
The unloaded fire maze room is 2600 units above the boss door room, and the two are connected by a huge vertical shaft. Intended to be traversed downward by knocking down this huge pillar with the megaton hammer at the end of the dungeon, this shaft has a room transition trigger around 80% of the way up which, when touched, toggles which of the two rooms, upper or lower, is loaded. Touching that transition trigger while being launched upward from the boss door room makes it possible to enter the fire maze room while it’s loaded, meaning its doors are usable, allowing progress to the final couple of rooms before the megaton hammer, minutes faster than normal dungeon traversal would allow.
The zombie jump that accomplishes this is an extension of the hookshot jump. When a hookshot jump is activated with death, Link dies before he leaves the ground, and the player has no control during the jump. This is insufficient for reaching the room transition trigger, but with ledge cancel active, Link's death is delayed by one frame. Dying on the same frame Link leaves the ground allows the player to retain control until Link hits the ground again ([zombie walking]), so combining a hookshot jump (using the heat timer to die) with ledge cancel makes it possible to move Link just far enough to hit the room transition trigger as he ascends the dungeon while dead, then land up in the fire maze room to be revived by a fairy.
This video discusses the history and discovery of the trick. Different strategies for preparing and executing this trick are shown below.
The Darunia Cutscene is activated when the camera faces Darunia's direction in that room. Timestop can be used to lock the camera in a way that the camera faces the opposite direction by holding target as you open the door. If done correctly, you can navigate to the small key without watching the cutscene. If your camera moves in a way that it loads Darunia, the cutscene will start immediately. It is possible to climb a ledge and hold target as the cutscene starts to skip the majority of the cutscene, as you regain control after a few text boxes. This can be useful if you want the bomb/fairy pots on the right side of the room (see second video).
It's especially fast to set this cutscene skip up with bomb timestop because you can run through the entrance room while waiting on the bomb. However, this can make it difficult to deal with the fire keese, and it may not always be ideal to take damage here if the heat timer is relevant.
As seen in the videos above, avoiding triggering the cutscene with timestop leaves Darunia in place, and re-entering the room normally still triggers the cutscene. For the cutscene to be cleared, the Darunia actor needs to successfully delete itself, which happens just after the sound of the boss door closing as long as Darunia is loaded. When watching the cutscene normally, this always happens, but if the cutscene is playing while you have control of Link after climbing a ledge during the cutscene as described above, then you need to keep Darunia loaded by keeping the camera facing roughly towards the boss door until it makes the closing sound.
In the video below, the cutscene is avoided with timestop, then triggered while Link is grabbing the hookshot target. Link then climbs the hookshot target during the cutscene, which causes it to give control back after a few seconds. Bottling a fairy brings up text boxes that clear the rest of the cutscene text, advancing it immediately to the ending animation of Darunia sliding through the door. The door is then kept on screen until the sound effect, at which point the cutscene is cleared, and re-entering the room doesn't trigger it.
Ledge cancel isn't too tough to time setupless, but it can also be done with this setup. Climb, dry roll, shield drop a bomb, backflip twice, hold up + shield + target.
If you don't have the hover boots, begin by getting ISG off the nearby fire keese. Killing or at least shielding the keese afterwards can be helpful, but it's still possible for the other keese to be a nuisance. Next, get ledge cancel with a bomb and the platform by the stairs. You can tell you got ledge cancel successfully by how the camera acts when Link moves around, but it's easy to be certain you got it if you press target and the camera fails to center behind Link. Last, if you're doing a setup that uses [Return A] to traverse the boss door room in first person, use another bomb for that.
These options are both trickier than they sound if you have ledge cancel without using Return A to make the camera follow Link normally, or if you're moving in first person. With ledge cancel, all inputs remain relative to the initial camera angle when you entered the room, then switch to be relative to the camera angle when Link reaches the hookshot target. The camera can shift erratically, but trying to move the same way and target at the same points every time make the camera more consistent.
Getting the boss key early is trivial with a weirdshot. Savewarp to leave, or use the method below to hit the switch using Hammer + Giant's Knife.
It is possible in the first room to clip through the hammer blocks off to the right. This can be done with several methods that are explained on the clipping page. Almost all of the time, this is done with a jumpslash clip. This is banned in Glitchless.
You can simply jumpslash clip through the blocks with the correct angle and position. An easy setup is shown in the video below.
Get into the left corner of the door and blocks and align the B button with some of the chains on the door (see video for exact position). Pivot 180 degrees and drop a bomb (some kind of chu set up would work as well). Pivot back and push forward until the bomb hits you and you are boosted forward. On this frame hold up-left on the joystick to clip through the blocks.
The block is not actually blocking the door, so it is possible, in the left side of the main room, to get up to the ledge without using the Song of Time to move the block. You can perform an angled jump and hold toward the ledge in mid-air to grab the ledge. Alternatively, you can hover up the platform, or you can do a megaflip from the platform that boosts upward into the air.
It's possible to jump from the lower left platform to the boss door platform because of [remote wall interaction]. For the jump to work, Link needs to be in the corner, right up against the wall that the boss door is on. See video for details; jump shown at 2:17.
This trick allows you to skip from the "green room", with the pushable block and crystal switch, directly to the switch that opens the Goron gate in the same room. This bypasses going up to the boulder maze, getting 2 keys, and ascending to the upper portion of the maze before going back down to the Goron.
There are several methods. The most common one, shown first, uses damage from a bomb. There are also methods that use bombchus and methods that avoid taking damage (using roll invincibility), for routes that are on low health.
This strat relies on jumping from a specific part of the floor with the torch slug (very lenient, shown in image below video). Once you grab the ledge, face directly upward (usually an ESS turn) and pull a bomb. Get into the corner and release everything before the bomb explodes. Hold left after the bomb explodes to move towards the inbounds area. You can also hold target while holding left.
If you fail the strat, you can get the angle again without jumping back to the ledge. See the backup video linked here.
If you miss the target room, you can attempt to steer yourself to some out of bounds collision and jump into the void to get back to the green room. See this video for a reference.

In Glitchless, clipping is banned so the above strat is not allowed. You can still skip pushing the block through the green room, however, by jumping to it with a bomb push. The tutorial below demonstrates this, with a non-initial backup linked here (although, the position for climbing the ledge is not precise and can be eyeballed).
It is possible in the large fire maze room to get through the fire walls, which skips needing to use a key to go through the middle room. There are several ways to do this:
If you superslide or HESS roughly perpendicular to the fire walls, you have enough speed to get through them. When going from the pit to the big flame wall to bypass it with damage invincibility, HESSing is around 2-3 seconds faster than supersliding, mostly because a bomb can be pulled during the HESS but not during a superslide. It's also more feasible to HESS off of a bomb thrown from the pit before climbing out than it is to superslide off of one, and a 2-bomb superslide uses one more bomb than a HESS does.
The only upsides to supersliding are that some may find it easier and that after failing a HESS or superslide once, it's easier to avoid the rolling boulders retrying with a superslide than with a HESS.
The angle for the superslide isn't precise, but climbing the wall for facing angle 0x4000 and then doing 2x ESS right to 0x31f0 is a reliable setup.
This is the easiest method. Simply roll or backwalk along the wall. This can be eyeballed, but the video also shows cues for where to start moving to avoid getting knocked down. When going from the pit to the big flame wall to bypass it with damage invincibility, this method is around 5-6 seconds slower than HESSing.
A sidehop from a good position along the wall can get Link through the fire. Sidehops make it harder to avoid getting knocked down than using rolls or backwalks does, but it is still possible.
To defeat flare dancer, first jumpslash to store jumpslash damage on your power crouch stab. When the flare dancer jumps out of the center and starts spinning, hookshot it out and then crouch stab. Repeat this twice more (if using Master Sword) to finish the fight.
There are several important things to know about the fight:
If you need to jump down to the Song of Time block room, but you don't have more than 1 heart to survive the fall, you can do this strat with a hammer jumpslash to avoid taking damage.
These all utilize a ledge clip.
Requires a good diagonal notch. If you target after the hammer text box and sidehop right instead of turning, targeting the chest, and sidehopping left as the video shows, then you stand a better chance of avoiding the fire keese if it's coming for you.
Note: if you are trying to back up the ledge clip because you failed the clip and grabbed the ledge normally, there are faster setups shown in the next section.
Alternatively:
Note the important untargeted ESS up input after the two dry rolls, if doing the trick unbuffered.
The fastest method uses a HESS with the correct angle.
If you fail by jumpslashing too early, you may land in the unloaded fire maze room. From here, you can do the ledge clip boss key skip from the fire maze room.
A bit easier than the HESS but slower. This can also be done a bit faster with an initial setup from the Hammer chest, shown in this video.
Ledge clip in the corner shown, then target, drop, jumpslash, and hold up to reach the load zone quickly.
It can be done when the room is unloaded as well, for example as a backup for a Hammer room BK skip, as demonstrated here.
On the right side of the room, climb to the top of the ledge near the hookshot tower. Get ISG and carefully hover down the long passage using bombs and bombchus. Who you reach the room Darunia was in, hover backwards until you are above the boss door. Then backflip into the Boss Door loading zone.