Things You'll Need
Instructions
Slide a piece of cardboard under the completed jigsaw puzzle and transfer both to the cutting mat.
Cut the cardboard around the jigsaw puzzle to create a frame that will keep the puzzle from shifting during the gluing process.
Cover the entire work surface with newspaper. Slide a second piece of cardboard under the puzzle and place another piece on top of the puzzle. Carefully flip the puzzle and transfer the puzzle-cardboard sandwich to the work surface, with the puzzle face down. Slide out the bottom cardboard and take off the top cardboard. Place the cardboard frame created in Step 2 around the puzzle.
Spray glue on the back of the puzzle.
Place the stiff paper backing over the glue and smooth out any wrinkles. Cut the paper backing to the exact size of the puzzle with the knife.