In a dutch oven over medium-high fire, heat oil to hot and add flour. Stir constantly to make a roux. Roux is ready when it reaches the color of a tarnished penny. Now add onions to roux (the color will darken a lot but it is not burnt), stir often until onions are clear, about 10 minutes. Add bell pepper and green onions and cook for another 5 minutes. Add water, celery, sausage, and 1 tsp of fil?. Bring to a boil and then lower fire to medium-low and simmer for 45-50 minutes. Add seafood and Cajun seasoning (or salt & pepper to taste) and continue cooking for 25-30 minutes. Skim grease from top of gumbo and add remaining fil?. Ladle over a bowl of hot rice and eat like a soup. Serve with a sidedish of potato salad and crackers. For a delicate flavored gumbo, omit the smoked sausage and add 1 lb of catfish fillets (cut into nuggets) 10 minutes before the gumbo is ready. NOTE: Gumbo is always better the second day so make enough for leftovers! Also good as an appetizer served in cups.