I had a hen, Sassy, who was an excellent broody. I had taken a few of her eggs and finished incubating them over a day or two (She got off the nest early maybe, I wasn't sure, so I took and incubated the remaining eggs after she hatched her first two.) I put fake eggs in the nest instead, and she kept sitting on them, so I decided to try and reintroduce the chicks once they hatched.
Her hatchlings were only a day or so old, and only one of the remaining eggs hatched, so I brought it outside to give it to her in the middle of the afternoon. I wasn't going to be around in the morning at first light, and wanted to see if she'd take the baby while I had time to make other arrangements if she didn't. I put it in a cup to carry it so I wouldn't drop it by accident. It was cold, and cried. Sassy heard the chick when I was outside the covered coop/run, called to it, and waited on the nest with her other chicks while calling stridently to the new one. I got inside the run, crawled into her enclosure, grabbed the chick up in my hand, and shoved it under her, in full sight of the hen. I grabbed the fake eggs from under her, and pulled them out in the same swipe. She never pecks me, and didn't this time either. The chick immediately got warm and stopped crying. Sassy stopped calling to it, and everything was quiet. No issues. I checked on them over the next few hours, and no issues.
Sassy was like, give me ALLLLL the chicks!!! and didn't care where it came from. It was a chick, therefore it was hers. I love that hen!
I did a number of things differently than how most folks recommend to do them with chick introductions. But it worked fine for my particular hen. Would i recommend others use the same technique? Not necessarily. Introductions at night are still best practice. Every hen is different. You just have to try what you think best and see how it goes.