The Boards are finished!
Have added extra debris of various grades, to parts of the boards, to look like land slippage, or piles of builders rubble, and painted to blend in. I then sealed the boards with varnish, before adding silflor tufts and other greenry to represent small areas of scrub.
I tried to add the extra debris/green foliage in a logical fashion, in areas where any surface water would have run off, but ultimately it was added to "look right".
Hopefully I managed to avoid teh temptation to add too much - it is supposed to be a semi-arid desert region afterall!
The next stage is to create some extra add-on scenary, in the form of a few trees, and larger bushes, for snipers to hide behind - these won't be integral to the boards, so as to make storage/transportation easier.