I’ve made some puzzles with three tiers giving it a 3D effect. I wrap the end of the three blanks together (the extra board that won’t be cut with the puzzle) or you could use a couple of bolts and nuts. Then I glue the puzzle picture on the top board. I make an extra black and white copy of the puzzle picture and draw the pieces I want to cut, I do this because I’m not good at cutting the pieces on the fly, but I want to be strategic where I cut the puzzle. Then I place the black and white copy exactly on top of the colour puzzle picture and use clear packing tape and wrap it around all the boards. It’s not a perfect solution but it works for me, I start on one side and cut toward the end with the extra board.
Irene