Since their invention -- arguably by manufacturer John Spilsbury -- people have enjoyed jigsaw puzzles. One is often filled with a since of accomplishment fitting the final puzzle piece in place and seeing the whole picture, but then questions what to do with the completed puzzle. After spending hours making it whole, you don't want to tear it apart. A creative solution is to frame and display the finished product, making the puzzle a decorative object.
Place sheet of foam core on a flat surface. Assemble puzzle on top of foam core. Cut the foam core to the size of the completed puzzle.
Place poster board on top of completed puzzle, sandwiching the puzzle between the foam core and poster board. Carefully slide one hand under foam core while pressing down in centre of poster board. Flip over and remove the foam core. You should now have the puzzle, picture side down, on top of the poster board.
Apply spray adhesive to the backside of completed puzzle and firmly attach the foam core. Alternatively, you can cut a large sheet of clear adhesive paper to the back of completed puzzle. Either way you have now permanently assembled the puzzle pieces together.
Place the puzzle, picture-side-down, inside the frame. If a mat is needed to fill out the frame, place it inside first.
Place the backing board on top of puzzle and close framing assembly. If you didn't use foam core, you may need to add additional backing between puzzle and frame to ensure the puzzle doesn't slide.
For extra security, you can apply several coats of clear-drying glue to the puzzle's picture side. Allow to completely dry before flipping puzzle. Completed jigsaw puzzles do not always match the dimensions stated on their packaging. You can trim them to size, or to square, using a sharp utility knife and a rigid straight edge.
Acidic backing paper will eventually discolour your puzzle. Choose acid-free foam core to avoid this.