So I took another go at the design from the triangular ‘wooden’ one except, well, not triangular but square (the Islamic Art book had both options). Unfortunately I ran into much the same problems as before:
Maybe it’s not obvious, but the small triangles are all different sizes, and the many many 12-fold shapes are all off. So I got annoyed with it …
Naturally I then painted over with various shades of brown, to try and get a wooden effect, which did not work. Therefore I tried some coffee!
Because why not, right? It did not work very well really - unsurprisingly! Worth a try (it might do something interesting in other circumstances, I guess).
Just to see if it could get any worse, I then varnished the heck out of it:
I really didn’t need the graphite on top, but still. Oh well.