we have the same problem here on the coast... all we have is rocks everywhere under the top inch of soil. We built our coop in the woods (both for shade and aesthetics ) and used the trees as our posts. We did use chicken wire (i know a lot of people have issues with it but we've never had predator problems and it's more to keep the hens in) and wood that we cut down to make the space for the run. We've had our hens there for a year and they're happy and very safe and it was relatively inexpensive.