Lightly grease slow cooker. Add water to the slow cooker, then whisk in flour.
Arrange chicken in the slow cooker in a single layer, then top with tomatoes, mushrooms, olives, capers, capers, garlic, salt and pepper, Italian seasoning, and chicken broth. Cover and cook for 6-7 hours on low OR 3-4 hours on high.
Uncover slow cooker, add spaghetti noodles, spinach, and tomato paste, stir to combine. Cover and cook another 15-20 minutes. Stir again and serve topped with cracked black pepper, fresh thyme, and grated parmesan cheese if desired.