I've just finished slapping on couple of layers of paint on some craters I made out of MDF and Jovi (air dried modelling clay).
You know those silly sabot city sections I made a while back? Well, the MDF bits that I cut out to fit in the vac form plastic craters in the city sections I kept (and a few more from another couple of industrial type sections I'm working on), seeing as they were crater shaped, purchased some air dried clay to build up some crater walls around them. Not particularly robust (the clay shrinks as it dries, and cracks when bent back into shape), but with some PVA and a couple of layers of paint...well, we'll see how they last!
Ironically, I can't use them in the sabot bases themselves, as, well, the fit is too tight! They'll be good for additional atmosphere and cover during Epic and Crossfire games.
And hey, I had these cool crater bases, so...why not?!