On our 19 I used white 1/2" Taco Marine Starboard (HPDE Plastic) material then installed two 9"x5" vents and a small handle to lift and maneuver. The vents help in keeping the boat a little fresher inside. I transferred the teak trim piece at the top of the original factory board to give it a little more bling, and to better match a similar piece on the sliding hatch itself. That trim piece is totally optional. toI like this material since it's impervious to rot, strong, easy enough to clean and doesn't splinter, ding, or otherwise appear to show any signs of wear. If you do scratch it up over time you just sand them out--no "refinishing" work. It's still one piece but have thought about cutting it into two for easier storage. I have read that some folks have had problems with this material warping but no problems here in the 6 years I've had it here in the sometimes very hot and very cold but not extremely bright sun midwest.
The downside is the material is heavier and more expensive then similar size plywood, and perhaps a little harder to cut/shape/sand than wood, but not having to do much maintenance on it is a plus--there is enough work to do without adding something else. I think you can get it in white, black or tan.
I tend to do projects and little changes, so this winter I'm making a lower half board out of Meranti marine ply and kevlar fabric for use underway some of the time. In fact I just epoxy laminated the two 4mm panels today. There will be a flush mount compass along with holders for an iphone and another gadget or two on the board for easy viewing. The jury is out if I'll stow it separately or use it in tandem with another half for the upper area. Leaning towards just keeping the one piece Starboard hatch and stowing the compass/gadget half board separately, then mounting when needed. I figured this way I won't have to drill a bunch of holes for a large compass (Richie BN-2-2- Navigator) and some gadgets-and they will be very visible front and center. I can probably step right over it and into the cabin on the 19 as well.
There should be a pic of the starboard hatch somewhere in the link in my signature if you're interested to take a look. The white board is not for everyone, but I like how it looks and love the low maintenance factor.