Don't let wood get bent out of shape
Freshly resawed or planed stock will certainly warp when allowed to lie facedown on a flat surface for as short a time as one hour (even faster in dry climates). Moisture will escape from the exposed face of the board at a faster rate than from the side facing down.
Stand the piece(s) on end so air can flow along all surfaces. Leaving wood this way overnight allows the stock to restabilize.
—From the WOOD magazine shop