One day in advance, soak the beans in water overnight. Make sure to cover the beans with at least 4 inches of water. Soak for 8 hours or up to 48 hours.
Drain and rinse the beans when you’re ready to use them. In the slow cooker, add beans, enough liquid to cover them by at least 2 inches, garlic, cumin, and salt.
Cook on low for 10 hours.