“This is a very simple meal to make. You just throw everything in the crock pot and let it cook during the day. I like to serve this over thin spaghetti (especially garlic and herb thin spaghetti when I can find it).”
Place chicken in a slow cooker; stir in spaghetti sauce, tomato paste, mushrooms, onion, bell pepper, garlic, oregano, basil, black pepper, and red pepper flakes. Cover.
Cook on Low until chicken is tender, 6 to 8 hours.