I don't think there's a single, easy way unless you just happen to get lucky and they all accept each other. "Pecking order" is hard wired into chickens and they need to sort it out. In my short experience, I've decided that the best we can do is provide good methods to integrate new chickens, watch out for excessive violence or food / water deprivation and have lots of patience. This summer, we integrated four new chickens....2 each from different sources. These two, separate pairs were integrated into an existing flock of 4 mature birds. The 4 mature birds were two Red Stars, one RIR and one BR. The BR was the "queen". The newcomers were 2 Buff Orps and 2 Auracana's. Here's what we did.
1) The Buff's went into a small pen in the barn. The Auracana's went into a large dog crate right outside the pen. They stayed like that for a week.
2) After a week, I hand carried each of them outside the barn well away from the coop where the mature birds were, and let them free range. After a while, the four birds forgot that they were wary of each other and hunted bugs together. If they got TOO close, one would peck the other. After a couple of weeks of this, they all went out and came in together without any help at all. Essentially, they were a new flock.
3) By this time, the 4 new birds were getting close to the physical size of the other 4, mature birds. I believe that it's important to integrate when their sizes are somewhat equal (sometimes, that will never be possible). So, I moved the four new birds into the coop with the others. I did this at night, per the often prescribed advice. All was well.....during the night.
4) The next day, the 4 new birds tried everything to get out. They were pecked mercilessly by the older birds unless they stayed on the roosts. The 2 Auracana's succeeded in getting out and, every day, they would exit the coop into the pen, get chased by the older birds, fly over the fence and free range all day. Soon, the Buff's learned to do that as well. So, I added fence.
5) Two full weeks went by with the new birds staying inside and the older birds moving around as they pleased. The new birds stayed on the roosts. When the coop wasn't being used by any older birds, the newer ones would hop down and eat or drink. I added a waterer outside to reduce the trips into the coop by the older birds.
6) After two weeks, I tried to force the situation by pushing the new ones outside and locking up the coop. I also gave them lots and lots of scratch, watermelon, cabbage, cherry tomato's, grapes....you name it. It really didn't matter much. Patience is a virtue.
7) Two more weeks go by and I open the coop at 5:30 AM one morning. First chicken out is a Buff. Hmmmmmm. Odd. Later that day, I have 6 chickens in the pen. The 2 Auracana's still like the coop.
8) A week after that, the two Auracana's are out as well. We now have an 8 chicken flock.
9) This past week, one of the Buff's started laying and both Auracana's started as well, although one thinks that the best place to lay is right in the middle of the pen...outside....in broad daylight. She's the most skittish chicken and I think she's doesn't feel secure enough yet to share a nesting box next to one of those "other" chickens.
For me it was: separation with viewing; common reason to share space (free ranging); integration with protection (places to hide, roost and eat/drink); and patience, patience, patience.
Finally, our coop is 6X8 and it's 8' high. Like a shed. It has 3 nesting boxes and 3 roosting areas. The nesting boxes stick out, like a traditional coop so the inside space isn't compromised. It's PLENTY for 8 chickens.
Hope this helps!
