Many years ago made a few using modeler's plywood. Once the board was cut to fit, I put it into a sealed plastic bag that was filled with Elmers white glue. Let them sit for a few days, and then took them out and wiped their surfaces clean. Some of the Elmers had "soaked" into the inside of the boards. After a few days they completely dried out. Final sanding with the finest emery? sandpaper that I could find. At this point they would not stain all that well, but this procedure actually added some rigidity/firmness to the plywood. Definitely preferred them to "rip off" Technika boards made with questionable metals.