Open frame test track baseboard
open frame baseboard ply
There are detail differences but it's basically the same pattern. No corner braces on the top face because I don't think they add anything and no holes in the ribs because, ahem, I forgot. But since the frame is open the holes are probably redundant anyway and they don't affect the weight much - I can lift the unit with one finger.
I need to make one more similar board and a simple bridging piece to complete my roundy-round test track.