I have a 4" by 4" frame atop 4" by 4" posts into concrete patio blocks. Posts make adjustments for terrain height trivial. I put 6" galvanized drip edge between frame and coop to deter water and critters.Couple questions for you:
1. Is your coop on skids, piers or how is it elevated?
2. What did you do underneath it? I mean, landscape fabric, mulch, plastic, gravel or just plain old yard underneath?
My ground is thin topsoil on porous gravel. I added course mulch and then blown in fall leaves; rinse and repeat. Each fall I fill the space, flock goes berserk with joy. Maintenance free, I never touch it.