Google sand in coop it’s a game changer!!!!
My entire coop is 6 inches of dry sand. No flies no smell. I have a nice warm perch and no draft but controlled ventilation. I scoop each day. Amazing so happy with it and so are my 4 ladies.
As a general rule, sand works well for people in dry climates -- if they don't mind daily scooping -- and horribly for people in wet climates.
The article I linked above includes a pros and cons list.