Heat olive oil in a large skillet over medium high heat.
Add thinly sliced sausage, and cook, stirring frequently, until lightly browned, about 3-4 minutes.
Place sausage, minced garlic, diced onion, diced carrots, diced celery, drained beans, oregano and bay leaves into a 6-qt slow cooker.
Stir in chicken broth and 2 cups water until well combined; season with salt and pepper, to taste.
Cover and cook on low heat for 7-8 hours or high heat for 3-4 hours.
Stir in spinach until wilted.
Serve immediately.