What is the best way to preserve a puzzle?

K: What is the best way to preserve a puzzle?
1) Peel and stick technique
2) Puzzle glue on the front of the puzzle
3) puzzle glue on front and back of the puzzle
4) puzzle glue on the front and peel and stick on the back

Please tell me what you have used and how well it worked. What did you and/or dislike aboput the technique you used?
I want to make sure it does not get damaged and I want it to stay together long term.

Answers and Views:

Answer by thejanith
Puzzle glue on the front and back is your most secure option. It lasts the longest.

Answer by HOOK
I like to give TWO coats of Mod-Podge glue on the front, then I mount mine to a 1/8″ piece of Plywood then into a wood frame with plexiglass cover. That’s if you want to hang them as I do.. Otherwise coat the front and back,