Dice the onion and mince the garlic. Add the onion and garlic to the slow cooker along with all the other ingredients and stir 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.
