Last post included a foam mound masquerading as a scenic break / mountain. I wasn't 100% sure on how to make it look more like the start of a slate cliff face,  so I googled lots of pictures before bed and woke with a plan. A few extra pieces of packing foam through the saw on my lunch break and a bit of spray glue later....

I'm pretty happy with it as a startling point, with the addition of some tghisck grey floor leveling compound troweled on and shaped I think it will start to "take shape"