You are dealing with living animals. You don’t get guarantees with them.
I’ve done it with chicks I hatched in an incubator, always with chicks maybe 2 days old at most. I’ve put some under a hen at night after it was well dark. I just cupped them one at a time in my hand and slid them under her. When I checked the next morning everything was quiet. She raised them fine.
Once I waited until the hen brought her chicks off the nest, then put her in a pen. I caught her chicks and put them in a box then added several more to the box. When I dumped the box in front of the broody she didn’t seem to notice her chicks had gone from 4 to 15.
Some broodies will accept about any chick at any age, but the older the chicks the less likely most broodies are to accept them. She might accept week old chicks if you slip them under her at night, but I’d be very sure to be there first thing the next morning to see if she was mothering them, killing them, or abandoning them. I’d be real nervous trying it with week old chicks. With some hens they will be OK but to me that is getting real risky.
Another problem is that by a week old the chicks have not bonded with that hen. The chicks may not want to have anything to do with her.
A hen will peck a chick to discipline it but they can also try to kill one that way. I sure can’t tell you which that was way over here on the internet.
I’ve seen a hen get chicks down from a 10 foot high hay loft. When Mama says jump, they do, then bounce up and run to Mama. I don’t suggest you put a broody up that high, but when Mama decides it is time for the chicks to leave the nest, she’ll hop down on the ground and tell her babies to join her. They will.