The night before, pick over the black beans to check for stones and rinse them well. Put them in a large bowl or pot and cover with at least four inches of water.
In the morning, drain and rinse the beans and put them in the slow cooker. (Be sure to rinse the beans well. By rinsing and discarding the soaking liquid, you are eliminating most of what causes flatulence after eating beans!)
Add the rest of the ingredients, except for the salt, and cover with broth. Set the crock pot to either high for about 4 hours, or low for about 8 hours. (If you have all day, use the low setting. Cooking the beans slowly makes them exceptionally tender.)
Before serving, season with salt to taste. Enjoy with warm tortillas, salsa, cheese and any other garnishes you would like!