Dice the onion and mince the garlic. Add the onion and garlic to the slow cooker, along with all the other ingredients to the slow cooker. Stir the ingredients in the slow cooker to combine.
Place a lid on the slow cooker and cook on high for four hours (or low for 8 hours). After cooking, the lentils should be tender. Taste the chili and add salt to taste, if needed (this will depend on the salt content of your broth).
Serve the chili hot, with your favorite toppings.
*I like to use coconut oil because it has a similar mouth feel to animal fat, but it does give a slight coconut aroma to the chili. Feel free to use your favorite oil or fat in its place.