Combine the soup ingredients. Add the garlic, green bell pepper, onion, basil, oregano, Parmesan, crushed tomatoes, tomato paste, chicken broth and red pepper flakes to the slow cooker. Stir to combine, then nestle the chicken breast into the broth. Do not add the pasta yet.
3 cloves garlic, 1 green bell pepper, ½ cup white onion, 1 Tbsp fresh basil, 1 tsp dried oregano, ½ cup Parmesan cheese, 14.5 ounces crushed tomatoes, 1 Tbsp tomato paste, 4 cups chicken broth, ⅛ tsp red pepper flakes, ½ pound boneless, skinless chicken breast