It depends on how far you are throwing the feed as to how big the ring is. I have 2 that are made of 3/4 in PVC, 2.5 ft x 2.5 ft. with 4 elbows to make it a square. I have one on my bigger pond that is 5 ft. x 5 ft. I would just take some 3/4 in. black tube/hose and make a circular one if I did it again. Join the two ends and anchor it down. At one time I used a hula hoop. Worked great, unless the wind was blowing really hard, it would rock the hoop enough that the feed got out of the hoop.
If I were you, I would look into buying a Native Outdoor feeder. They work great and run about 80$. It has worked great at my place. You can read many other posts about them.
