In a perfect world, you would encourage the chickens to focus on one physical area at a time by either having a mobile coop which moves every few days to a week - they tend to forage more near home than far away - or some sort of fencing that gives them paddocks that they are
led to, again they can go to a paddock for a time period based on how quickly they're consuming what they want to consume and that can change based on the weather and the time of year. Chickens *don't* like eating poopy grass - can you blame them? "Mob grazing" improves pastures according to all sorts of studies, far better than letting animals stay in one place regardless of how large the place is. Those studies are usually looking at cows or similar, but it works with chickens too.