Place the uncooked rice, chicken, onions, celery, carrots, garlic, bay leaves, chicken broth, water and seasoning in your crockpot. Cover and cook on high for 3-4 hours.
In the last 30 minutes of cooking, take our the chicken breast and shred. Then add shredded chicken back in the crockpot.
Melt the butter and oil in a pan and add the flour. Let cook for about a minute. Then slowly whisk in the milk until all lumps have dissolved. The mixture should thicken and be creamy. Add tot he crockpot and stir to combine.