DO-AHEAD TIP: Sort, rinse, and soak beans overnight.
Drain, rinse and drain sorted and soaked beans and place them in a slow cooker with the broth and water.
Cover and cook on LOW for 8 to 10 hours or on HIGH for 5 to 7 hours. (NOTE: If beans take longer to cook, it could be because they are old.) Thirty minutes before serving, heat the olive oil in a large skillet over medium-high heat; add onion, bell pepper and celery and sauté for 2 minutes; add green onions and sauté for 1 minute; add to bean mixture along with remaining ingredients (thyme through corn).
Cover and cook on HIGH while you prepare the rest of the dinner.