How should I bury hardware cloth? (Picture included of spot)

How deep is the trench? Assuming it's deeper than any predator will dig to get under I would just put the cloth straight down into the trench and attach it to the outside of your fenced in area. The goal is to stop diggers like Coyotes. If you have a raised coop so the birds can go under it then I think the general rule for a run is about 10 square foot per bird. And inside the coop is 3 square foot per bird of floor space. Depending on how many birds you want I think you can fit quite a few. I'll let you do the math

 

Its not going to take long for the hardware cloth to rust away to nothing. I was able to get cull lumber (treated) from lumber yards and box stores. It didn't matter that it wasn't pretty or straight since it was all buried. It was attached to the posts and extends about a foot below the surface of the ground. I did the same to the barn since it was built on posts.

 

Doesn't galvanized hardware cloth last longer? Or not?

 

I lined the entire bottom of my run with regular poultry wire and so far is holding up well. It goes to the foundation blocks all the way around. Never had any predators get in as of yet. I have a couple inches if gravel then a few inches of sand on top of it. Occasionally, the girls will dig down and expose a little bit of it so I just cover it back up. This spring I'm going to add a couple more yards of sand to top up also. It tends to settle and run away a bit for the first year or two.