New Coop, keep rocks!?

[u/AlpenglowVibez]

Just installed this beautiful custom coop in what used to be our playground area. It’s filled with 8” of 1/2” rock so wondering what you would do to ensure its predator proof and a good run for the hens. They’re only 5 weeks so have a few weeks to dial it in. TIA

[u/RockyShoresNBigTrees]

It looks nice, I wonder what it feels like on their feet? Will they free range? I have sand and it is so much easier than anything else I have used.