To make this you will want a skillet, a 6-8 quart Dutch oven or soup pot, and a 3 quart sauce pan.
Prepare your ingredients: chop the onion (keep the onion separate), the celery and the bell pepper and slice the sausage.
Peel and season the shrimp with some Creole seasoning and put in the fridge.
Start warming the stock in the smaller sauce pan.
Add the 1 cup of oil and the flour to your Dutch oven. Make the roux over medium to high heat, stirring constantly, until the roux reaches a dark reddish-brown color for a Cajun-style roux (this will take a half hour or more). If you want to save time, or prefer a more Creole-style roux, cook it to a medium, peanut-butter color (a dark roux brings more flavor, while a lighter roux is a better thickener).
If you make your roux over a low heat, you have less risk of burning it and you can work the other skillet at the same time. If you make the roux over high heat, it will take less time but you will need to stir it continuously. If you burn the roux (you will see the black flecks in it) it will be ruined and you will have to throw it out and start all over again.
When the roux is nearly done, add the chopped onion and mix into the roux; this cooks the onion and slows the roux down. Cook these until the onions caramelize and the roux is a glossy dark brown, another 5-10 minutes.
Add some of the hot stock to the pot, a ladle at a time and incorporate with the roux. When you have about 2 quarts of stock added to the pot, bring it to a boil stirring continuously to thicken with the roux.
Season and brown the poultry (if uncooked) in a large skillet with some oil. Shred if needed and then add to the pot.
Brown the sausage in the same oil, and then add to the pot.
Brown the celery and pepper in the same oil, adding more if necessary. Add the garlic at the end. Add to the pot.
Brown the okra in the same oil to remove the moisture and stickiness. Remove and put in a bowl and then in the fridge.
Deglaze the skillet with some of the stock or some wine and add this to the pot.
Add any remaining stock, the bay leafs, thyme and Creole seasoning to the pot; taste and adjust the seasonings as needed. (If making this over two days stop here and reheat before picking up the next day).
Simmer for 2-3 hours (I like to put it in a 250 F degree oven.)
Start the rice - if it gets done ahead of the gumbo you can hold it in a warm oven or the microwave.
Add the okra and the whites of the green onions to the pot and cook for 30 minutes.
Add the parsley and the tops of the green onions and cook for another 15 minutes.
Add the shrimp and cook for the last 5-8 minutes if using cooked shrimp, or 20 minutes if using raw shrimp (so, if using raw shrimp add it at the same time as the onion greens and parsley).
Place a scoop of rice in large shallow bowls. You can add filet powder for a little more thickening and for another level of flavor.
Serve with some crusty bread and a good beer.