I have a flat back bass in pieces. One side of the flat back is detached from the glue line. Over time this flat piece of wood has warped and is no longer flat. Now my problem is how do I get this piece of wood back to flat or near flat? The warpage is significant. I was thinking of placing it on a flat hard board and placing heated sand bags on the wood, as well as a bracing system that will keep it flat until I need to glue it. Just an idea. What do you guys think? Any suggestions?