Add rinsed split peas, broth, diced ham (or ham bone), diced carrots, diced celery, diced onion, and minced garlic to the slow cooker.
Add bay leaves, dried thyme, salt, and black pepper, then stir everything together to combine.
Cover and cook on low for 8 hours or on high for 4-5 hours, until peas are completely broken down and soup is thick and creamy.
Remove and discard bay leaves and ham bone if using (shred any meat from the bone and return it to the soup).
Stir well, taste and adjust seasonings, then serve hot with crusty bread or crackers.