I always wanted to do a rocky ground like this, but getting them sloped in random directions after creating a custom voronoi was a pain. Plus, getting the right surface contouring was tough too. For the sloping, I just did 4 different non-uniform blurs with assymetry in 4 different directions, them blending them together with the variance map. I multiplied the result into the rock map. Using the Liquid node as a slope in a slope blur node turned out to be a great way to control the amount...
