Adhesive for applying keyboard keys to wood I have a mosaic made of keyboard keys that I made by gluing the keys to a piece of cardboard. After some time, the cardboard has begun to warp under the weight of the affixed keys.

I now have a similarly shaped piece of plywood that I plan on affixing the keys to so it won't buckle under the weight and will stay flat when I mount it.

My question: What type of glue/adhesive should I use to affix the keys to the plywood?

I originally used tacky glue to affix them to the cardboard and that seemed to work pretty well. Would tacky glue also work in this case? Or should I use something like wood glue?
I always recommend two-component epoxy for this kind of bond (PE plastic with laminated wood), however if you have a lot  of keys it can get pretty expensive (and messy). 

A cheap approach would be to use plumbing silicon (the kind in the tubes). Put a drop in the back of the key and press it firmly onto the board. It should hold for a long time!