Hi! I usually feed my guardian dogs in the morning right after I feed my goats, while the goats are still eating in the feeders. My dogs have learned to eat fast and protect their bowls, and I feed the goats inside the barn and the dogs just outside.
My good friend has a corner in her paddock set up with a pipe gate to block it off. Her dog food dispenser (she free-feeds) is in the part farthest from the gate, kind of at the tip of the triangle. The dogs can squeeze through the pipes and eat, but the horses/goats/sheep/donkeys can't.
Hope this helps!