Cut the material
Cut the insulation into eight 24-inch squares. Plan on using two pieces for each target (producing a 4-inch thick panel), so one sheet of insulation provides enough material for four targets.
Glue two insulation pieces together with spray adhesive. Spray both surfaces to ensure a firm bond.
Glue a sheet of cardboard, cut to the same 24-inch square dimension, to one side of the insulation. This increases the durability of the target and helps stop the arrows.
Glue one of the floor mats to the cardboard. This will be the front side of your target.
Bind the edges with tape. Use two strips at each corner, going from front to back across the stack, is usually enough to keep the target together.
Wrap the block you just made in a plastic or canvas tarp or drop cloth (optional). Doing so catches bits of foam that will fall from the target as it's being used.
Place the 30cm FITA target on or onto the target butt you just made. This size target matches the size of the floor mat panels used.