Heat a large deep skillet to medium heat and add the olive oil, garlic and onion. Sauté until garlic is fragrant, add the sliced collard green leaves (you may need to add a handful at a time until they cook down as not to overcrowd your pan)

Cook greens, stirring occasionally until they are wilted.

Add the remaining ingredients and cook until the broth begins to simmer.

Transfer to a slow cooker and cook on low for at least 4 hours. The greens can be cooked longer than 4 hours- I tend to think greens taste better the longer they cook.