How do I put puzzle pieces in a picture frame?

Here's a really cute idea https://www.kiwico.com/diy/Arts-and-Crafts-Ideas/1/project/Puzzle-Piece-Frame/2248

Here are some ideas. http://www.sarajcreations.com/2016/11/diy-christmas-gift-ideas-puzzle-piece.html

I made a flat wreath and not a picture frame, but it would be the same idea. I painted the puzzle pieces in autism awareness colors and glued them on. This would work best with a flat frame https://www.yourbeautyblog.com/2018/03/diy-tulle-autism-puzzle-piece-wreath.html

Mod-podge the front and back at least once, the ones I help do 2 layers on each side, Measure your puzzle and buy a frame that fits. The backing works better with a lift off back than a slide on back. Make use the Mod-podge is completely dry before putting it in the frame. Hand on a 20 pound weight hanger for safety.

2 poster boards are suggested so puzzle stays in intact when flipping and use 2 or 3 people for flipping the puzzle during the Mod-podge process and inserting in to the frame. HAVE FUN!!