A good friend once told me... It's fricken plywood, it warps, it twists, it bows, ect... it will do this laying perfectly flat, hanging upside down or rightside up, leaning against a wall. You can build a perfect fram and lay it flat with weight on top of it in a vacuum sealed bag and the middle will probably pick up once the weight is removed.

Store them how you wish, when ready to use screw on the rails and the 60 plus pounds of hardware and put it in your game. Btw your pf will move in your game as well to a certain extent.