Remove excess fat from the chicken. Rub a generous amount of salt, garlic powder and red pepper on both sides of each piece, making sure each is evenly covered. Let stand at room temperature for 30 minutes.
In a medium size bowl combine the onions, bell peppers and celery and set aside. Combine the flour, 1/2 t salt, 1/2 tsp garlic powder and 1/2 tsp red pepper in a plastic bag. Add the chicken and shake until well coated. Reserve 1/2 cup flour. In a large heavy skillet heat 1/2 inches of oil until hot. Fry chicken until crust is brown on both sides and meat is cooked 5 to 8 mins. Per side. Drain on paper towels. Carefully pour the hot oil into a glass measuring cup, removing as many of the browned particles in the pan as possible.
Pour 1/2 cup oil and 1/2 cup flour into the skillet. Cook whisking constantly, until roux is dark red-brown about 3 1/2 mins. To 4 mins, being careful not to let it scorch or splash on your skin. Remove from heat and immediately add the reserved vegetable mixture, stirring constantly until the roux stops getting darker. Return pan to low heat and cook until vegetable are soft, about 5 mins, stirring constantly and scraping the pan bottom well. Bring stock to a boil. Add roux mixture by spoonfuls to the boiling stock, stirring until dissolved between each addition. Return to a boil stirring and scraping pan bottom often. Reduce heat to simmer stirring in sausage, chicken, okra and and file, adjust seasoning. Add rice to bowl or martini glass and ladle gumbo over the rice.