I've had a little bit of success in getting hens to accept 1 or 2 chicks at a time, but I've never tried it with a whole slew at once.
It can be helpful to isolate the hen (in a dog crate in the house) for a day or several, prior to introducing the chicks. Let her get bored in a quiet, dark place, nothing to do, but be sure she is very comfortable, favorite foods, lots of bedding. Then place the chick(s) in under her at night when she is groggy. But keep an eye on things carefully for that night and, especially, in the morning when she realizes fully that she has company!
One time I tried this, the hen beaked the chicks a few times, tossing them across the crate even, though it was just to get them away from trying to weasel under her. They became afraid of her, despite their urge to seek a mama, and stayed at the far end of the crate. She did, after a day or so, change her mind and decide they were incredibly lovable. You just never know. You will need to be very attentive, remove them/give up totally if she pursues them with aggressive intent. You cannot let them get cold if she rejects them at first or ignores them. Keep trying it in spurts, if she is mostly tolerant, keeping them warm in a brooder box in between sessions with the hen.
And, yeah, have a back-up plan! The 1st week is the most critical/fragile time for chicks. You could keep them in the house for a week, then move them outside (with a brooder/heat set-up, of course).