Chop your vegetables and set aside. A food processor works great as well, but don't add the green onions to that mixture. They'll be used at the end of the cooking as a garnish in the pot.
Heat the oil in a large, chicken-fryer sized pan over a medium to medium low heat. Add the flour after the oil is hot and stir constantly. (I used my handy-dandy automatic stirrer on the roux while I chopped the vegetables and it worked fine; had to stir a few times by hand because the stirrer made it clump up in the center at times. Also, I wouldn't recommend leaving the stove during the process, even with the auto-stirrer working on it.) Watch the roux carefully. It will gradually change to the color of melted milk chocolate. When it reaches that color, add about 6 cups of water, or whatever your frying pan will hold - you can always add more to the pot, if necessary.
Some folks add stock to their gumbo but it's not necessary, there will be plenty of flavor without it.
Stir the water in well and pour it all into a large soup pot. Cook this over medium heat as you prepare the rest of the ingredients.
Brown the meats, sliced into one inch rounds, in the same frying pan. If using smoked turkey meat in addition to sausage, this can be chopped and added right to the pot. After browning, place the meats into the pot of roux and water.
Using the same frying pan with a tablespoon or so vegetable oil added, saute the onions, celery, peppers and garlic until softened. Add Worcestershire sauce if desired (about one tablespoon) and spoon the vegetables into the pot as well. Cover and simmer for about 3 hours, stirring occasionally. Taste and adjust seasonings, adding salt and pepper to taste, some cayenne or hot sauce if you like, about midway through cooking.
Before serving, garnish the pot of gumbo with the sliced green onions. Serve in bowls with a scoop of rice in the center.