Use the ball & chain to destroy the lookout tower next to the fence, transform into a wolf, and walk through the gap. Then wedge Link through the right (GCN) side of the fence. This can also be done as wolf (dashing continuously) or as human (rolling repeatedly).
After triggering the bulblin archer cutscene, run over to the left (GCN) side of the barricade and wait for a little while until one of the boars runs into the wall, launching the bulblin riders onto the wall. As wolf, get close to the wall and use a Midna charge to target the riders. Walk back a bit from the wall and release the attack to superjump onto the wall.
Perform Map glitch, dash or roll up to the broken wall before the main part of the camp, and LJA from the corner of this wall to the hill OoB. From there, it is possible to jump attack diagonally to the King Bulblin trigger. The bulblin archer will shoot fire arrows at Link during the daytime but not at night; see setup for how to handle this. It is also possible to shoot a bomb arrow at the rotisserie boar through the wall to release the HP for later. This method is 3.5s faster than the other Map Glitch method described below.
Perform Map Glitch (this can be done just before climbing the wall while transforming to human, but doing it immediately after the load zone or archer cutscene allows for unplugging the controller)
Roll to the broken wall and climb up the left edge
Walk forward or charge a spin attack to reach the front edge of the wall
Sidehop right 3 times, making sure the bulblin archer shoots and misses during the sidehops
Aim at the corner of the hill and LJA over
Roll forward, line up (can use minimap), and jump attack towards the King Bulblin trigger, making sure to cross ground level out of bounds
After entering the Bulblin Camp, immediately perform Map Glitch and backwalk off the solid ground. Do a jump attack while falling to give Link forward momentum. If done right, Link will eventually hit the cutscene trigger, which will reposition him above ground.
Jump from a tent to a wall, LJA to another wall, and jump to the tent to trigger the King Bulblin cutscene, saving ~8 seconds over getting the key. The timing for the LJA is tight. This is the fastest way to enter the KB3 fight without Map Glitch.
It's possible to get on top of King Bulblin's tent with bomb boosts. This is slower than the LJA methods above.
Strats for Cave of Ordeals are now located here.