Start by prepping your collard greens. Pull the leaves from the stems. Discard the stems. I like to add them along with any other raw veggie pieces to a freezer bag and use them down the road to make broth. Tear the leaves into bite-sized pieces.
Wash and dry the collard greens.
Heat the olive oil in a large pot over medium heat. Add the onion and garlic and cook until the onion has softened. I find it helps to add a dash of salt to the onion mixture.
Increase the heat and add the chicken broth. Bring the mixture to the boil, then start adding your greens. Add as many as will comfortably fit, allow them to wilt down, then add more.
Add the ham bone or leftover ham pieces to the bottom of the slowcooker. Pour the collard mixture on top. Add the vinegar, sugar, salt, pepper and cayenne pepper and stir to combine.
Cover and cook for 4 hours on high or 6 hours on low.
Recipe by Hillbilly Housewife at http://www.hillbillyhousewife.com/slow-cooker-collard-greens.htm