So this is how I integrate my flock. I have a barn where all my chickens congregate at some point during the day. They’re completely free ranged though. So what I do is I put the newbies in my goat stall as my goats are rather friendly to young chickens. I leave them in there because the others can see them from the loft. Sometimes other birds will hop down there to snack on the goat feed and will casually introduce themselves. When the newbies feel confident enough, they come out of the stall and meander around the barn, slowly meeting the others. Once they’ve done that for a while, they venture outside. There are many places where the little ones can hide in case of bullying. Personally, I’ve had no issues. My flock ranges from birds ages four years old to a couple months old. If you want, you can have the young ones in a crate next to wherever you’re keeping the older ones so they can see and get used to the new ones before you put them in together.