This is not conducive to a good hatch...best get another box for your other hens and mark the viable eggs under broody, removing any new ones daily.Lol This is my nest box XD
It works, and one of my hens is setting on eggs. We have chicks growing! What's funny is that even the rooster likes to sit on the eggs, and he's kind to them. Haha
((Not all the eggs in the picture were viable. We discarded the bad ones. And the cardboard box is just temporary. I've got a nice coop in the building process currently.))
Sure cardboard boxes can work, biggest issue can be when they jump on the side and tip the whole ting over...often on top of themselves.