I just went through this, my nesting boxes are on the 2nd level of the coop with a pretty steep ladder up. So on the first night I put my chicks under the broody hen in her normal nesting box. Once I was sure they all bonded (about 48 hours in) I built a box in the bottom of the coop for them. I then took her chicks from her and put them in the bottom box, she came down right away and went right in with the babies. That being said I did hand raise the momma from a day old and we get along really well, she was somewhat trusting of me when I took her chicks.
It has been the cutest thing to watch my Virgin Mary hen raise her little babies.
I kept the chicks and the hen in the same coop with the flock and they have been great together.