In a large pot or Dutch oven, add oil, onion, carrot and celery.
Sauté until vegetables are soft and tender.
Add garlic and sauté for 1 minute longer.
Add chicken broth, uncooked rice, basil and pepper. Bring to a boil.
Reduce heat to low, cover and let simmer for 15 minutes or until rice is cooked.
In a small bowl combine flour and milk. Stir into the soup.
Bring to a boil and cook while stirring for 2 minutes.
Add chicken and cook 2 more minutes until chicken is cooked through.
Serve Immediately.
