I’m building a new coop 66” W x 92” L and an adjacent run of 92” W and 192 L. The area I am placing the coop is a little low in spots, which I will be filling in with soil. I will be raising the total area for the coop and run by about 12-18”. What is the best material or combination of materials for compaction for support under the coop and run, but also good for the chickens to peck and forage through?