I would put in something, to keep the poop from stinking and to give the chickens something to scratch through.I'm designing my own coop and building as I go.
1. I have poured a concrete floor for the run. After reading numerous threads in here I'm still confused if I'm supposed to cover the concrete with something that's changed out frequently. We will have 5-6 hens. Do I cover concrete floor with pine shavings and DE? How often does that get changed?
If it smells bad, add more dry material (wood chips, wood shavings, hay or straw, dry leaves, etc.)
I would try to let it build up at least 6 inches deep, and probably quite a bit more than than. But at some point it will be so deep it's a nuisance, so take out some or all of it (compost for your garden) and then continue adding more.
I would also put in anything that might normally go in a compost pile-- weeds from the garden, eggshells and watermelon rinds and other stuff from the kitchen, and so forth. The chickens will eat some of the stuff and scratch around in the rest. And over time, earthworms will move in and the chickens can eat them too.
If it gets matted down, you can turn part of it over with a pitchfork or shovel to make it easier for the chickens to scratch through. Hay and straw seem to mat more easily than wood chips or shavings, and shredded paper usually mats quite badly unless it is mixed with lots of other materials. Wood chips probably work better than any other single thing, but a mixture of materials usually works better yet.
Different people do things differently, so I'm just saying what I would do.