Okay, so instead of next to the pen, I should put the chicks IN the pen inside their own? Either way is OK as long as they're warm, safe from hens, weather, & predators.
And then after their 4-6 weeks, do the hole in the bucket method right? You don't need that if you have a safe cage. Block off part of the door so only chicks may pass.
(Sorry, first timer, want to do it right the first time! Lol) There's truly not a right way to do it.
If you have the space to put their brooder inside the coop, great. If they still need heat & electrical cords, then it's up to you to decide where they should be. (If you don't want cords in the coop, then better to have them sleep somewhere else. I bring chicks outside only on nice days when it's naturally warm enough for them to be out (temp requirements vary by age). That is my personal preference b/c I don't like heaters in the coop/run, but everyone's different. When the chicks are between 4-6 weeks - depending on weather, so earlier in the hot summer months - they are old enough to no longer need supplemental heat. (They will need good protection from drafts & a place to snuggle.)
The timing of when I move their cage to the coop/run varies due to the conditions.
1. Broody hen's chicks- go into the cage as soon as all the eggs are hatched. Door is opened around age 5-7 days. No worries about heat or bullying b/c mama does it all.
2.If nights are cool, then I have the chicks sleep in the garage brooder but take day trips to where they can see the flock.
3. Heat of Summer. The chicks' cage may move into the coop/run at 2-3 weeks old, so there's a longer intro period before I first open their cage door.
My coop is small & doesn't have the floor space to add a cage. My covered run is pretty much like a 2nd larger coop (when I add the winter "storm windows") & it's like a breezy screened room with hardware cloth in the summer. I feel the chicks are safe in there, so that's where I put their cage. There are a lot of night time predators, so overnight safety is another consideration. Some people have a small separate coop/run set up next to their regular enclosure just for chicks, broodies, &/or injuries. (I don't have that luxury, but would like one!) All they have to do is let the chickens see each other for a few weeks & then open the door one day during free range time. Like I said, you have to find what will work for you.
You'll have to watch your hens & their reactions. My hens are pretty used to chicks coming & going. They do not bully little chicks, but they will take offense if a young chicken tries to eat from
their bowl. That's why I provide a safe zone for the chicks when I 1st begin to open the door. I often first open the chick's cage door about a week after I moved their cage to the coop/run. I do it on a day when I can observe periodically. The chicks quickly learn to stay away from the hens while enjoying their new found freedom to explore. I've never had a hen draw blood, but it's tough to see them get those warning pecks. From age 8 wks to 20/25wks, the chicks form their own mini flock & hang back. They remind me of the teen cousins at family get-togethers. Part of the flock, but keep their distance. When they finally grow up, they'll share in all the adult activities.