rfielder,
Inkjet photos tend to be a bit fragile - easily scratched & such - which seems bad for a jigsaw so I put a clear laminate over the top. At first I got some 3 mil (tried thinner - not worth it) self- adhesive stuff. Now I've switched to a hot press so I use a laminate made for that.
Mark explains the basic cold process in his videos (Mark's Custom Puzzles on YouTube). Use Super 77 spray to stick the image down. Spray the board and the back of the picture, wait about 1 minute for them to get tacky. Smooth it down carefully, then cover with baker's parchment, a layer of craft foam, a board, and some weight and let it sit overnight to get fully bonded. If using something with a fragile surface like an inkjet print, I say add the clear laminate before you let it set up.
A tip for getting the sticky things in place right: put a sheet of baking parchment over the bottom layer (wood first, then image for the laminate). Leave about 1" at one end showing. Put the next layer over it and get it all lined up. Now smooth the exposed surfaces together (not all the way to the parchment - you're just tacking it down). Slide the parchment over a bit to expose more, smooth toward it, repeat untl done. The silicone treated baking parchment is
very non-stick so you can get everything lined up well. By smoothing down just a bit at a time you get fewer bubbles and it's easier to smooth them out.
The hot press method needs a t-shirt press bigger than your largest puzzle you want to do, some
very expensive heat conducting foam (it's called 'green rubber'), dry-mount tissue and a laminate that's temperature compatible. The ones I use are called Tri-Mount tissue and Digital Laminate. Both fuse at 195 so I set the press to 210 (need to get a bit above 195). Takes
forever for everything to come to temp before I can press a puzzle. If anyone's interested enough to spend $1,000 on equipment & supplies I can give more details.
Can you guess how I've spent my time since March?