One week ago, my Speckled Sussex Linda hatched a single chick. (Two out of three eggs did not hatch.) Linda and chick are in a coop section by themselves. There is a run coming off this coop section, and they spend a few hours a day outside where they have the run to themselves. The rest of the flock free range and get a chance to see the new addition and the broody mama while they are out in this run.
I absolutely would not let this chick out to free range at this stage. I know Linda would do her best to protect it, but I refuse to take a chance of something happening to the little one.
If I didn't have the luxury of this extra run and coop section, I would create a protected space somehow. Baby chicks are simply too vulnerable free ranging in a wild area such as mine.
Decades ago, I had a couple of bantams, Leonard and Louise. They were semi-wild and lived in the hedges and trees in my yard in a suburb setting where there were very few predators. An occasional possum, maybe. Louise disappeared for several weeks, and returned with eleven chicks. They all survived free-ranging to drive me nuts practicing their adolescence crowing at 3 am while roosting in the hedge outside my bedroom window.
A tame and protected backyard would be the only exception where I would let a broody out to free range with a baby chick.