Sliding Puzzle Backplate

This is a simple backplate using the same dimensions as the puzzle itself.

The square in the center has a very slight recession to allow ample space for numbers to slide over while leaving the edges raised enough to adhere around the edge of the main puzzle via superglue (or any other adhesive)

By gluing the backplate to the rear of the puzzle, the largest gapped version (0.3) becomes a great option because it gives the numbers the most slack to slide around while protecting the pieces against becoming too loose and falling out of their enclosure.