my older chickens have been free ranging since 8 weeks, I started them out by stringing some chicken wire around metal stakes outside their coop, so they had a 'run' from the time they were 6 weeks old. At 8 weeks I took a section down and they gradually began exploring, getting a bit braver each day.
I also have silkies who are only 6 weeks old now. They were in a sectioned off area of the coop inside. I took down their enclosure a week ago and they are gradually exploring, they go outside for an hour or two each day, staying very close to the coop. They all put themselves to bed each evening.
I've had great luck with allowing the chicks to decide how far to go. All of them were locked within the coop for over a week before I let them out so they definitely know it's home.
BTW I love freeranging! my older chickens spend the day on the front porch with us, always near us. So fun to watch and be with. They jump up and sit on our laps. They seem pretty smart as well, even crows cawing will send them running for the coop or under a bush. Good luck with yours.
p.s. I live in maine with tons of predators, we've been very lucky. The chicks are locked in like fort knox each night, so far (knock wood) no losses from my flock of 23 chickens!
I should add that someone is usually home. They haven't been left for more than a few hours so far. I think at this age if I were to go out for the day I would leave mine in the coop. We aren't always outside but we're in earshot. hope this helps, sorry the post is so long!