First, a note on the dangers of framing.
1. Gluing the puzzle down means you will never be able to play with it again. This method is definitely not recommended.
2. Displaying a framed puzzle means that the colors will fade over time. More light exposure will lead to more fading.
3. Having glass or plastic in contact with the puzzle risks damage to the puzzle surface over time.
A simple way to frame an assembled jigsaw puzzle without having to glue it down is to use a clear “box frame
”, easy to find in craft and frame shops. A box frame is not permanent, so you can take the puzzle out and play with it. Or replace it a few months later with your newest favorite puzzle.
* Note: A "box frame" is not the same thing as a "shadow box frame". A shadow box frame is not good for framing a puzzle.
A box frame consists of two parts. The bottom, is a 5-sided cardboard box that is sized to standard sizes for photos, and are about 1 inch thick. The top is a clear plastic lid. For example, the box could be 8" x 10" x 1" and the clear lid 8.2" x 10.2" x 1.2". Simply lay the assembled puzzle in the bottom box and put the lid down on top of it.
Get a frame that is a bit larger than the puzzle - for an 8" x 10" puzzle, get a 10" x 12" frame. Use some foamcore that is the same thickness as the puzzle pieces, and cut four strips from it, to center the puzzle in the frame. In this case 2 strips of 1" x 8" and 2 strips of 1" x 10" foamcore.
Finally, get a mat board and cut the opening just a tad smaller than the puzzle dimensions – in this case a 10" x 12" mat board with a 7.75" x 9.75" opening. The mat board is a spacer thus eliminating the risk of damage to the image by the lid.
To assemble, lay the puzzle in the box, roughly centering it; put the foam core strips around it; lay the mat board on top of the puzzle; and put the lid on top.
Since wooden puzzle pieces are thick, you may need to tape the edges of the lid to the box part of the frame to keep the lid securely on the box.
Guest blog from jigsaw puzzle historian Anne D. Williams