If you have a broody hen, let her stay with the flock. Her broody hormones will cause her to rise to the top of the flock. I swear my layers tiptoe around her. When the chicks hatch, the rest of the flock are rather like, "what did you do" and if any get too close, whew! She will clean their clocks. Then the flock accepts them, and mostly ignores them. I have seen them eating right between the legs of another chicken.
This works for me, but I will admit that I have lost some chicks, as in survival is of the fittest. They need to hatch, dry off and stick with mom. Those that do, do fine. Last fall in October, I had a hen hatch out 4 and raised them just fine, by herself in the flock. A week later it was -15F, and they did fine.
What often happens is the people following advice here, pull the broody hen so she won't be bothered while she broods. The flock forgets her, she does not belong to the flock anymore. Then people want to wait until the chicks get big to add them all back to the flock. Running out of room about 3-4 weeks. At this time the broody hormones are beginning to fall. The hen is beginning to forget her chicks, and with the best intentions the people put the whole group into the flock.
The hen is desperately trying to find her place in the pecking order, and the chicks (foreign to the flock) are free game and without protection. and it is a disaster.
Always have some hide outs available!.
Mrs K