If you make a ring of welded wire, chicken wire, or hardware cloth that is high enough that they can’t hop over it, you can plant inside of that. The flock can get their heads through welded wire, but won’t be able to reach the plants in the middle.
If you check out “Edible Acres” on YouTube, he uses this approach to grown everything from grass/clover for the chickens, to veggies, to sunflowers and small trees/shrubs.
If using this approach to grown grass/clover for the flock, you can even give it to them in sections by moving the setup off center (but still protecting part of the patch).