Stand on the rotating flower in the center and aim an arrow at the northwest corner where the unlit torch is located. When the fire crosses your path, shoot the unlit torch to light it and open the final door.
Start off by killing the Dragonfly and Skulltulas around the room. Now put on the Great Fairy Mask and shoot the bubble to the back left to get Stray Fairy #12 . Don the Deku Mask and go off to the east alcove to find Stray Fairy #13 .
Continue climbing up this side and you’ll find Stray Fairy #14 . Now go over to the west side where you’ll collect Stray Fairy #15 , that’s all of them!
Look across to the east and fire an arrow at the crystal to extinguish the fire. Fly into the covered area with the Deku Flower, then onto the pillar with the Deku Flower, then onto the eastern roof.
From here use the Deku Flower to fly to the ledge where the door is located, unlock it and head in.