1. In a shallow bowl, combine flour, salt, and pepper. Dredge chicken in flour mixture.
2. Heat olive oil in a large skillet over medium-high heat. Add chicken and cook until browned, about 5 minutes per side. Remove chicken from skillet and set aside.
3. Add onion and garlic to skillet. Cook until onion is tender, about 5 minutes.
4. Grease slow cooker. Place chicken in slow cooker. Pour onion and garlic mixture over chicken. Top with tomatoes, wine, chicken broth, Italian seasoning, oregano, and red pepper flakes.
5. Cover and cook on low for 6-8 hours.
6. Serve hot.