Add all of the ingredients except the salt to the slow cooker and cover with 4 cups of water. There should be about 2 inches of water covering the beans.
Cook on high for 3 to 4 hours, or on medium-low for 6 to 8 hours.
Remove the bay leaves and large pieces of onion and garlic. Drain any excess liquid from the beans, add sea salt to taste, and serve. (I like to retain any extra liquid and eat it like soup!)
Notes
If cooking on the lowest setting, it can take more than 8 hours to cook unsoaked beans. But you can turn the cooker on low, leave for 8+ hours, then increase to high to cook for about another hour and the beans will be soft.
When cooking beans and lentils, I never add salt or acid (tomatoes, lemon juice, etc.) until they're soft, as adding these ingredients early can significantly prolong the cooking time.