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. The three most common methods are explained 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.
This method is simplier. Simply get into the same position as the previous method, and triple stab the corner with the hover boots on. The third stab with the Biggoron's Sword allows you to clip through.
This method is even simpler. You can simply jumpslash clip through the blocks with a very precise angle and position. An easy setup is shown in the video below.
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.
In the first room with green walls, you'll come to a ledge with a crystal switch and a block you must push. It is possible to clip through the block and land in the lower corridor to open the shortcut to the top of the boulder maze early as well as a key.
When you jump to the ledge, put away your sword and walk into the corner where the wall and the block meet. Press Z against the wall to line yourself up with the wall, then swing your sword. Now turn right and grab the block then let go (you might need to move just a bit forward to grab it). Now swing your sword once more and charge to do a spin attack to activate the crystal switch. Now pull out a bomb and shield drop it (don't shield drop too fast, make sure its above link's head before dropping it) then walk back into the corner, line up again with Z and hold forward. When the bomb explodes, it should push you through and you should land in the tunnel.
This trick will occasionally not work even though it seems to be set up correctly. Sometimes moving very slightly to the left before the first sword swing will increase consistency.
If you make it up to the boulder maze bottom floor, you can get to the top by hovering. It is recommended you get one or both of the keys on this floor before hovering up, depending on your route. However, the above method is strongly recommended over this because its about 30 seconds faster and conserves bombs.
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:
Probably the easiest way, a simple sidehop from a good position along the wall can get you through the fire.
If you superslide perpendicular to the fire walls, you have enough speed to get through it.
Using incredibly precise rolling, it is possible to hover from post to post above the fire maze, thus skipping it entirely. Due to its incredible difficulty, it is only useful in a TAS.
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.