Make the Roux*: In a large, heavy bottom stock pot combine flour and oil. Cook on medium-low heat, stirring constantly for 30-45 minutes. This part takes patience--when it's finished it should be as dark as chocolate and have a soft, "cookie dough" like consistency. Be careful not to let it burn! Feel free to add a little more flour or oil as needed to reach this consistency.
Brown the sausage, chicken, and shrimp. In a separate skillet on medium-high heat place the sausage slices in one layer in the pan. Brown them well on one side (2-3 minutes) and then use a fork to flip each over onto the other side to brown. Remove to a plate.
Add the garlic, celery, jalapeño, bell pepper, and onion and cook for one minute.
Add the beer to deglaze, then add the stock, thyme, bay leaves, cajun seasoning, and 1 teaspoon black pepper. Stir slowly and continuously
Bring to a simmer and cover. Cook, stirring occasionally, for 3 hours. Gumbo should thick but not like gravy. Season with cayenne and serve with cooked rice. Top with scallions and enjoy.