In a 4- to 6-quart slow cooker, stir together beans, vegetable stock, 2 cups water, onion, carrot, garlic, oregano, thyme, parsley, rosemary, black pepper, red pepper flakes and bay leaves. Cover and cook on low setting for 8 hours.

After 8 hours, remove and discard bay leaves. Directly in the bowl of the slow cooker, use a potato masher to mash the bean mixture a few times (this will thicken it slightly but leave most of the beans intact). Add tomatoes, zucchini, spinach and salt. Stir well until spinach just starts to wilt; then cover and cook an additional 20–25 minutes on low. Stir in about ¾ of the Parmesan right before serving. Garnish servings with remaining Parmesan.