In a slow cooker, combine the rinsed navy beans, chopped onion, minced garlic, diced carrot, and diced celery.
Pour in the chicken broth and add the dried thyme, bay leaf, black pepper, and salt. Stir to combine.
Add the smoked ham hock or diced ham to the slow cooker.
Cover and cook on low for 8-10 hours or on high for 4-5 hours, until the beans are tender.
Once cooked, remove the ham hock, shred any meat, and return it to the soup. Discard the bay leaf.
Adjust seasoning as needed, then ladle the soup into bowls and garnish with fresh parsley before serving.