Just before the checkpoint located in the Skittler-filled tree is a large, rotating, grass-covered platform. After you kill the third flying Tiki Torch, the Puzzle Piece will appear. As each platform rotates into a position that you can stand on, you have to crouch down, blow the flames out of the flying Tiki Torches, then jump on them to kill them. You will come across a series of rotating wooden platforms, with flying Tiki Torches floating between them. Puzzle Piece 4 is rather deviously hidden.