My hubby built me a Chicken 'Salad' Bar out of scrap lumber and chicken wire a few months ago and here is an update on how it worked.
I used the Omega 3 Forage seed mix from Peaceful Valley and scattered seeds under the wire and watered for a few days. It grew quickly and very lush and the chickens enjoyed it for about 6-8 weeks before it needed re-planting. I moved it out of the area, let them dig up the remaining plants and just re-planted it. I love this because it is a great way for them to get fresh greens when they are locked up in Chicken Park.
The outside of the chicken salad bar is surrounded with random bricks and it is about 6 inches tall which is perfect. We tried it about 2 inches off the ground but the chickens weight smashed the wire down and they ate the roots of the plants quickly, so lesson learned on that one!