I got this idea from Bee and it's worked well for us:
At first, I just used the three-foot piece of vinyl gutter on the ground. It worked amazingly well, they didn't tip it over as often as I thought they would. Recently I added the wooden ends and brace strip to make it into a more stable feeder. They can't tip it over at all now and should last a long time.
As Bee mentioned, don't use galvanized gutters, as the acids in the fermented feed will leach out the metals.