In dutch oven melt butter over medium heat.
Add onions, bell pepper, celery and garlic.
Saute vegetables until soft, about 30 to 45 minutes.
Add Crawfish tails and seasonings.
Cover and simmer for 10 minutes.
Mix flour in water, stirring to make a smooth liquid.
Add to crawfish mixture, cover and simmer for 10 more minutes. Serve on hot rice.