Another way
is to groove the ply like Larry did (only I used a table saw set to just cut less than the first layer of the ply) and then to fill with white wood filler from Home Depot. It comes in a plastic tube. I first stained the ply, then applied a THIN coat of satin varnish, then cut the grooves, then filled using a putty knife to squoosh the filler in and leave it a little proud, then sanded with a finishing sander to take off the excess filler. Finally, eight coats of satin varnish. Inditinguishable from teak and holly. If you want to brighten up the interior, use a maple or oak stain and mahogany filler, reversing the pattern. It works!Any way, either method is great. Good luck.