Spray 6-quart slow cooker with cooking spray. In 4-quart Dutch oven, heat oil over medium-high heat. Stir in flour with wooden spoon; cook 6 to 8 minutes, stirring occasionally, until caramel colored. Reduce heat to medium. Stir in onion mixture, bell peppers and garlic; cook 4 minutes. Add wine and 2 bottles of the clam juice, stirring to loosen brown particles. Pour mixture into slow cooker.