It seems impossible to find a flat piece of plywood in my medium sized town.  This is shopping at commercial specialty lumber stores, not the big boxes.  On a good day I’m looking at ~3/8 inch of bow; on a bad day twice that, even after picking through a pallet’s worth (needless to say I’m not popular there anymore).  Is there an easy (or for that matter any) way to make a piece of plywood flat?  Thanks!