I have today fitted all the chicken wire and doubled up to 6' and did as you say, set it 12" down from the posts with 12'' at right angles then filled in with three inch of concrete then topped off with soil packed down.
My sheep dog Jud stays at my allotment and will chase and kill everything that gets in
Rabbits, rats, woodiesand all lol.
the only thing I'm worried about is the sparow hawks that vist now and again.
I have a very big barn owl nesting in a box I made for him up a tree above the chicken coop I'm making, so I covered the roof in chickien wire just to be safe.
I have never seen a fox down there but I'm sure Jud would see them off if he saw one