Remove the top shells of the crabs along with the deadmen (gills) and discard. Crack the crabs in half, reserve.
Heat the oil in a large 8 qt Dutch oven until smoking, about 5 minutes. Gradually add the flour and cook over high heat, stirring constantly until the roux is the color of milk chocolate, 3 to 5 minutes; Being careful not to burn.
Add the garlic, onions, bell pepper and celery and cook for 5 minutes until wilted. Add in tomatoes, cayenne pepper, herbs, and bay leaves. Cook about 3 minutes.
Gradually add 3 quarts of stock to the pot, stirring constantly. Add the crabs and okra. Bring to a boil. Reduce the heat to a simmer and cook for 1 hour; skimming often. Add the shrimp and cook for 5 minutes.
Add the crabmeat, oysters and their liquor and bring just to a boil over moderate heat. Add Worcestershire, hot sauce and salt and pepper to taste. Serve immediately over the rice and garnish with green onions and dusting of file.