Well I finally decided to tuck into the third board
Although rather unlike the other two I glued patches of sand, not an entire board's worth.
Here it is:
I noticed that in the plans I designed a road system, which seems to have been replaced by huge amounts of sand OOPs :( .
I did a spraying session, which might have included orcs and some other terrain features, but the can ran out just before I finished spraying this board section.
So one patch looks more sandy than black.
Definitely will have to get some more spray paint, for the final square of board, orcs, the Shadowlord and other terrain features.