My experience of introducing chicks to existing flock.
I have twelve production reds, 6 months old and all laying.
About 5 weeks ago I bought 10 production red chicks (3 weeks old).
After reading lots of threads on this forum (thanks to all), this is what I did.
Inside the coop we built a small moveable cage, with 1/2" welded wire sides and a removable plywood top, I kept the chicks in there for about 5 weeks, in full view of the older hens.
During this time we constructed a moveable pen out in the run, (made this out of four old bug screens wired together, and a sheet of plywood on top, in case it rained and also to keep the hens out.
In the mornings when I let then hens out into the pen, I put the chicks into their pen, so they can then scratch around and get some sun and fresh air.
The hens are let out to free range at about 10 am, and the chicks then go into their little pen.
Yesterday I decided it was time to try to mix the chicks with the hens. When I let the hens out into their pen in the morning, I let the chicks run with the hens. One or two of the hens chased the chicks a little and there was the odd peck.
When I let the hens out to free range, I put the chicks into their own little pen, so I could leave the gate open if the hens wanted to get back in to eat or whatever.
That evening when the hens had gone to roost, I put the chicks in the main coop. IT WORKED.
I have done exactly the same again today.
I will take it day by day and maybe in a week or two, I will let the chicks out with the hens to free-range.
This has been my first experience and maybe I have been lucky, I don't know.
Once these chicks are free ranging we will get another ten and do the same thing.
Hope this helps.