I then transferred the pattern for the base of the seat to some MDF board to make the bucks to form the seat bottom. The buck required two pieces, one the size of the seat base and one slightly smaller. The edges of the smaller board were smoothed and chamfered with some 80-grit sandpaper. I then laid out the base pattern on the aluminum sheet and cut around the pattern leaving an extra 3/4 inch to fold over the buck. I sandwiched the aluminum between the two MDF bucks and C-clamped the two together as tight as I could (this is important so that nothing moves on the next stage). I left the front edge with no C-clamps to fold over first.