If you don't clip their wings, they're going to fly right over whatever fence you put them in. I've had pullets roosting 14' up in the rafters before.
Wing clipping is easy and just as painless as clipping your own fingernails.
We have woven wire fence and yes, sometimes our birds find a way under. When that happens, we put a big rock under the fence at that spot. Sometimes we have to watch for a few days to see where they're getting out. Sooner or later, you'll find all the low spots and they'll stay in. It just takes...