I'm not sure what your situation is like, but if you are mostly just concerned about bears, while you were at work, I would just free range them. I don't believe a bear would chase a chicken so they are better off where they can run, instead of being stuck in a place where they are trapped in the bears path.
I'm sure there are other predators to be concerned with so I suppose that would be a personal choice...
If you really don't want to free range them, I would suggest a large run, with bear strength electric fencing around it. I can't remember where we got ours, but we were having trouble with bears destroying our beehives and an electric
fence did the trick. I do remember the website was specifically geared towards bears, if that helps. It was a kit, 40'x40', with the posts and all, took half a day to set up...