I have a puzzle I got from Disneyland about 10 years ago, and some of the pieces are lifting so I decided to glue it together and frame it.
First I moved the puzzle on plastic covered cardboard in case glue seeped between the pieces. I bought puzzle glue that included a scrapper. Use wax paper under the edges for glue runoff.
Glue and scraper. Note: always follow the instructions on product. The one I used, recommends not putting glue on the front if it glows in the dark.
Pour some glue in the center of the puzzle. Don't use a lot, you can always add more if needed.
Use the scrapper to pull the liquid glue from the center to the edges. Keep a thin even layer. Don't get to much glue over the edges.
Keep pulling the glue to cover the puzzle. Scrap off any excess.
Let dry for a few hours or overnight.
When dry, flip over puzzle. It will be easy since one side is glued together. If glue gets on the wax paper, be gentle when removing the wax paper from the puzzle so it doesn't get ruined.
Glueing the back of the puzzle will give it extra stability.
The process is the same as the front use. Pour a small amount of glue in the middle.
Spread it out in a thin layer.
Keep spreading a thin layer until the whole back of the puzzle is covered.
Let dry for a few hours/overnight.
Why dry, gently remove any stuck wax paper/plastic. Insert in frame. Enjoy!