I've raised several batches of CX -- usually 20 to 25 at a time -- in a closed 8x8 shed with access to a large yard. The shed was a simple converted storage shed with, hardware cloth covered windows and a concrete floor. I put packsaddle (wood) pellets as first layer. That helped with cushioning and moisture absorption. I then topped with straw.
My strategy was to feed them twice a day as they got older. I put their morning feeding outside, and after all the cx rushed out after it, I would close the shed up. At night, I would put their second feeding inside the shed and they would all rush back in.
Every morning, after they were 4 or 5 weeks old, I would shovel a matted top layer of straw off and refresh the straw. They generated a lot of compost, but we have a big garden so it all got used. With fresh straw each day, they stayed clean.
I would also put out old produce and some sprouted grains around the yard, to keep them moving. The yard never got over soiled.
As they approached 8 weeks, the shed would get pretty crowded, and that's when I would start butchering them in stages - the biggest 5 or 6 first -- wait a week, and then take the next largest. By 12 weeks I would be done.
I've since moved to raising rangers or dual purpose heritage breeds, because I like the flavor and overall experience of raising them better. But, boy you couldn't beat the CX for how fast they turned feed into meat.