Slow Cooker Chicken Tikka Masala

Name: Slow Cooker Chicken Tikka Masala
Ingredients: 2 tablespoons extra-virgin olive oil; 1 cup onion, chopped; 6 garlic cloves, minced; 1 tablespoon fresh ginger, minced; 2 15-oz. cans diced tomatoes; 2 tablespoons tomato paste; 1/3 cup water; 1/8 cup flour; 1 tablespoon garam masala; 1.5 teaspoon paprika; 1 teaspoon curry powder; 3/4 teaspoon salt; 1/2 teaspoon cayenne; 1/4 teaspoon black peppper; 1.5 lbs boneless, skinless chicken thighs, excess fat trimmed, cut into 1 inch pieces; 1 cup light coconut milk; 1/8 cup fresh cilantro, chopped + more for serving; 4 tablespoons Yogurt (Dairy-Free if preferred)**, for serving; Brown Rice or Naan, for serving; Salt & Pepper