After spending time completing a puzzle, preserve it by gluing the pieces together. This will allow you to display the puzzle by hanging it up on the wall in a frame. It may take a few hours to complete the gluing process, because you want to let each layer of glue dry before applying the next.
Assemble the puzzle fully on a piece of cardboard or wood. This will allow it to be moved easily if necessary.
Apply a thin layer of puzzle glue to the top of the puzzle using a brush or sponge. If you don't have puzzle glue, you can use regular white glue. Allow the glue to dry completely.
Apply three more layers of glue, letting the puzzle dry completely between applications.
Turn the puzzle over and apply a thin layer of glue to the back side. Allow it to dry completely.
Place something heavy, such as books, on the puzzle to flatten it if it's warped or bent at all.