Some suggestions.
You could put in some "raised beds" and plant what ever grasses, weeds that will grow in your area. If you took some fencing that was open enough for grasses and weeds to grow through but not open enough for their little heads to get through then planted long growing grass and weeds they could munch on that and bugs would come and they could eat those. Making a "hoop" over the top of the bed.
Now I also suggest some compost piles. More than one would work. Toss in some branches and green stuff and some chickens stuff and leaves or brown stuff. Cooties would come and they would have a ball scratching and digging. You could toss in some cardboard and get green stuff from the gorcery store, things like veggies out dated stuff like that. Bagged brush from the neighbors who don't use pesticides.
If it's big enough you could even rotate. Block them from one till the weeds and green stuff grows a bit and then let them have that one and block the one they were using til it grows up a bit. Buy late seasoned veggie seeds and just toss in all the seeds and let them grow. Things like lettuce and cabbage and kale.
It's really not something you would need to manage other than making sure it gets the water to grow the weeds and plants. Card board would hold moisture and draw worms and bugs.
I saw a program once where there was a flock of chickens that lived at the local compost pile. They lived there all year. Even in the winter. They were a wild flock of chickens. More like a dump really I think. I can't remember where I saw it.
Here is a pic of mine. I had to fence the garden in but you don't. You could just let the chickens have fun digging and dusting and all that. By putting in wet green veggies and dirt and chicken stuff and cardboard, worms may come and bugs. Trust me they will have a ball. In between my beds was wood chip mulch but they took care of that. I had to shovel the soil back into the beds.
I get apples and macaroni from the school I volunteer at that is stale and I get pumpkins and squash and also day old "bird" bread from the bread store. Costs me $1.25 for a bag of about 5 loaves of whatever they have. I put it in the freezer until I need it. Anything that is safe for them to eat can be tossed onto the pile. Scour the farmers market for lettuce and cabbage leaves pulled off. Give them a rinse and toss those on the pile.
Hope I've given you some ideas,
Rancher