I think if it were me I would wait till the chick hatches and then that same night or next night if she hatches at night,
*I would slip the new babies under her when all was quiet and still.
*Make sure none of the others in the flock can bother them. Its good if they can see them but just not touch.
*Then first thing just before daylight hits I would go to the coop and observe how she is with them.
*Just make sure the new chicks are not more than a couple days old.
Good luck!
Marie
Thanks so much! We got 6 day old chicks from the feed store this morning so fingers crossed it will work. Momma is on lock down brooding the the barn (apparently a favorite spot as it was where she was hatched as well), which is sheltered away from the flock, but when they come out to play/learn they see everyone. The rest of the flock has been through this last fall and everyone did well so hopefully will this time too, just haven't eer grafted chicks. Praying it takes!! I don't really care to be brood momma is she is willing!