I use shoe mats! Easy to scoop off if you do often, otherwise if I skip a while I just load them in a wheel barrow or something similar, cart it to the field and dump them. Then I just spray them down with the hose and good as new! Since this picture I have added 2 more so the whole area is...
More then likely they’re not frozen.. if they freeze they crack open. I am in Minnesota, we had actual temps hitting -30 last week, my eggs froze then. That’s the first time they have! Chickens are way more hardy that ya think. ;)