The wooden panels I use are constructed of 1.5 x 1 inch lengths of pine, with glued lauan plywood (durable, frequently used for flooring, siding or furniture) as the painting surface.
The nailholes filled, and sides are spackled and sanded.
The mitered corners are screwed together with one-inch waterproof screws, filled and sanded again.
Larger panels have reinforced cradles.
Finished panels are coated with a coat of gesso, allowed to dry, and a total of three coats are applied before starting the painting. The above are stacked to dry, just about ready for a new show of 16 paintings.