Off to a great start then.
My shed/outbuilding is raised and framed w/2x6s on a slope. We have problems with critters living underneath it. Mice and snakes, mostly. I like deckblocks, but they do make it hard to add skirting to deter those critters due to the way they flare out. You will need something, otherwise critters will use the space under the house as shelter, and your baby chicks, if they ever get loose, will decide that's exactly where they want to hang out when you go to catch them/gather them up and place 'em back in a pen.
On that thought, if you are planning on a brooder box/grow out pen in your coop, you should give some thought to where to place it, or how to make a temporary one on those rare occasions when you need it. It can be as simple as hardware cloth attached to a frame, hinged to store flat, but able to be shaped into an L and attached to two walls to complete the box. Use the short "side" as your door for access. Mine are all run floor to 4' high, but my adult birds can, and sometimes do, hop the fence, which isn't good. Next time, I'll set it on top of something else, like cabinet storage, so as not to waste space while making it harder for the adults to intrude. Wouldn't need to be so tall then, either.
The barn, and my hen house, I both took to ground level, so nothing could live underneath. And while I didn't add a layer of hardware cloth or similar to deter digging creatures, that's the typical solution.