Pour chicken stock into a large pot, and add ham hocks onion, garlic, red pepper flakes, vinegar, black pepper, and enough water to cover ham hocks. Bring to a boil; reduce heat, and simmer for 1 to 2 hours to create the broth.
Remove ham hocks from broth. Pull meat from hocks. Add meat and collard greens to the broth. Simmer for 1 to 5 hours, depending on the texture you prefer. Salt to taste, and serve with hot sauce.