In a large pot (I use a Dutch Oven), add the celery, corn, onion, and olive oil.
Allow to saute over medium heat for about 5 minutes, or until tender.
Add in the minced garlic, chicken broth, water, and 1 cup milk. Mix to combine.
Add in the pepper, oregano, bay leaf, and shredded chicken. Allow mixture to simmer over low heat for about 15 minutes.
In a small bowl, combine the remaining 1 cup milk with the flour. Whisk until free of clumps.
Pour mixture into the soup and whisk until combined.
Add the box of rice, including the seasoning packet, and mix well.
Allow mixture to simmer for about 20 minutes, or until rice is tender.
Adjust flavor with desired amount of salt and pepper.