After you invest hours of work putting together a 5000-piece puzzle, the last thing you want to think about is taking it apart. If you just can't bring yourself undo all that hard work, consider preserving the finished puzzle. You can use Mod Podge brand's Puzzle Saver or another decoupage glue to hold the pieces together.
Slide a piece of cardboard or newspaper under the puzzle to protect your table.
Dip the sponge brush into the glue or squirt the Puzzle Saver glue directly onto the puzzle. If your brush is too wide to fit in the container, pour a little bit of glue in an old dish or plastic bowl.
Spread the glue on the puzzle in a thin layer. Use just enough to coat the entire face of the puzzle.
Allow the first layer to dry completely. Apply a thicker second coat and allow it to dry. You should be able to slide the entire puzzle from side to side and it should feel fairly sturdy.
Flip the puzzle over carefully. Use the piece of cardboard to help you flip it upside down and then slide the cardboard back under the puzzle.
Coat the back of the puzzle with glue and allow this coat to dry. This should make your puzzle sturdy enough to transport and display.