Step 1: Rinse the dried navy beans thoroughly under cold running water. Place them in a large bowl and cover with cold water by at least 2 inches. Let them soak overnight (8-12 hours). Alternatively, you can use the quick soak method: bring beans and water to a boil, boil for 2 minutes, then remove from heat and let sit for 1 hour. Drain and rinse thoroughly.
Step 2: Dice the onion, carrots, and celery. Mince the garlic. If using a ham hock or ham bone, prepare it by removing any excess skin or fat if desired, though some fat adds flavor. If using leftover ham, cube it into bite-sized pieces.
Step 3: In a large skillet or Dutch oven, heat a tablespoon of olive oil or butter over medium heat. Add the diced onion, carrots, and celery. Sauté for 5-7 minutes until softened, stirring occasionally.
Step 4: Add the minced garlic to the skillet and sauté for another minute until fragrant. Be careful not to burn the garlic.
Step 5: Drain and rinse the soaked beans. Transfer the sautéed vegetables and drained beans to your 6-quart or larger slow cooker.
Step 6: Add the ham hock or cubed ham, chicken broth, bay leaves, and dried thyme to the slow cooker. Season with salt and black pepper. Remember that ham can be salty, so be conservative with salt at first; you can always add more later.
Step 7: Stir everything together gently. Cover the slow cooker and cook on LOW for 6-8 hours or on HIGH for 3-4 hours, or until the beans are tender. The longer cook time on LOW usually results in a more flavorful and tender soup.
Step 8: Once the soup is cooked and the beans are tender, carefully remove the ham hock (if using) and bay leaves from the slow cooker. Discard the bay leaves.
Step 9: Allow the ham hock to cool slightly. Shred the meat from the bone, discarding any skin or excess fat. Return the shredded ham meat to the slow cooker.
Step 10: Taste the ham and bean soup and adjust seasonings as needed. If the soup is too thick, you can add a little more broth or water. If it's too thin, you can mash some of the beans against the side of the crockpot with the back of a spoon to thicken it slightly. Serve hot and enjoy!