If you want to get good results, seperate her from the other chickens! I made the mistake of letting a hen set in the main coop, and had all sorts of problems with her getting kicked out of her nest by another chicken wanting to lay an egg, going to a different nest and letting her own eggs get cold. I think she had about 8 eggs under her, and only one hatched. All the others were fertile, and several were at different stages because the other hens sneaked them into her nest at various times during the three weeks. The little lone chick was picked on by the other chickens mercilessly and ended up dying. I will never make that mistake again! The broody's seperate quarters can be as simple as a large cardboard box or dog crate, as long as it is kept somewhere safe (such as in a garage, where dogs and predators can't get to her) Broody hens don't need much space, just a place for their nest, a little bit of room to stretch when she takes a little break, and a place to put her food and water. Good luck!