In a large pot, heat the oil over medium-high heat. Add onion and cook until translucent. Add the garlic and cook for 1 minute, stirring occasionally. Transfer to a slow cooker.
Add the black beans, kidney beans, chickpeas, corn, diced tomatoes, and tomato paste to the slow cooker. Season with the chili powder, cumin, paprika, cayenne, coriander, salt, honey, vegetable stock, and lentils.
Stir and slow cook on high for 4 hours or on low for 6 hours, until the lentils have softened.
Enjoy right away or freeze up to 6 months in an airtight container. Defrost in the refrigerator and reheat when ready to eat. Serve with shredded cheese, sour cream, and sliced scallions.