How can I design my PCB to mount to a wood panel without wasting a lot of space on screw holes?
Depending on board size and layout, you could mount it with 1 or 2 screws in the middle portion of the board rather than 4 screws at the corners. I've seen several devices that either aren't bothered by a small misalignment, or that use 1-2 screws plus pegs to achieve tight alignment without adding much to the footprint.