- Submerge the collards in a large bowl of water and swish them around vigorously to remove the grit. Drain the greens, then repeat 2 more times. (Collards can be very dirty.)
- In a large pot, combine the ham hocks and stock. Add water if needed to cover the ham hocks. Bring to a boil over high heat, then reduce the heat to medium-low and simmer until the meat just starts to pull away from the bone, about 30 minutes. Add the red pepper flakes and greens to the pot and cook over medium-high heat until the greens are tender, about 1 hour.
- Serve the greens along the potlikker and pass the pepper vinegar for diners to add to their taste.