oh, if I had chicks coming (I do) and had a broody hen, I would be thanking the Gods. Just leave her alone, the tighter she sticks to the nest, the better the mother she'll be. Leaving her alone is the key to a good broody mother. A lot of times, people trying to be careful interference cause more problems than they help.
When you get the chicks go down in the early evening, you want the layers roosted up, it needs to be dark. The chicks need to peeping madly, and this sounds heartless, but let them get a little cold, this makes them more active and peep loudly. Leave them like this for an hour. Then in the complete dark, with a flashlight pointed down, just enough to barely see. Place a single chick on her back. If the chick is a day old, he/she will disappear, or stick them underneath her. Those cold chicks will burrow in like ticks. It is their movement, and their peeping that flips the hormone from brooding to being a mother hen. The hen should start to growl and cluck to them.
This is the hard part. Shut up the coop and leave them alone to figure it out. Sometimes people go down, get everything stirred up, and then say the hen won't take the chick or is a mean mother. They interfere, and that confuses the chick and the mother, and pretty soon no bond is made.
A hormonal broody hen, will whip the layers, and raise those chicks right in the flock. If you have enough room in your set up, it is the best way of raising chicks.
Mrs K