Make sure that your ingredients, utensils, and pots are laid out and convenient before turning on the stove. This recipe moves quickly and relies on constant whisking so having everything laid out will help keep you from scorching the roux. I measure out all ingredients and cut vegetables, as well as 1 small saucepot, 1-8" or 10" skillet (no larger unless doubling the recipe) for the roux, and a second large skillet for the shrimp.
In a small bowl, combine the salt, cayenne, pepper, basil, and thyme. Set aside.
Bring 2 cups of the seafood stock to a boil. Turn down heat but keep hot. Cook the rice as directed.
In a 10 inch skillet or slightly smaller, heat the oil over medium high to high heat until it begins to smoke (looks like very slight steam), about 4-5 minutes. Gradually whisk in the flour until smooth. Continue whisking constantly until the flour is a red brown color, about the color of a new penny. (3-5 minutes) Immediately remove from heat (don't just turn off the burner- remove it!).
Add the celery, onions, and bell pepper. Add ½ (about 1 Tbsp) of the seasoning mixture and stir until well combined.
Over low heat, gradually add the pre-heated seafood stock into the roux, and whisk until combined. Continue whisking constantly and simmer a few minutes until any flour taste is gone.
In a large saucepan or pot over medium heat, melt the butter. Stir in shrimp and sauté until just pink on both sides.
To the shrimp, add the remaining seafood stock, the roux mixture, and the remaining seasoning mix. Stir until well combined and hot, about 4-6 minutes.
Serve in bowls with a ½ cup of rice. Sprinkle green onions over top of the dish.