Make the sauce first. With a fork, stir the Creole seasoning and salt into the flour.
Melt the butter in a saucepan over medium heat. When it begins to bubble, stir in the seasoned flour and make a roux, stirring constantly, until it's medium brown. (Be careful not the let the roux burn; throw it away and start over if it does.)
When the right color is reached, whisk the roux into the stock until the roux is dissolved. Add lemon juice, Worcestershire, and vinegar and bring to a light boil. Cook until thick enough to coat a spoon (five minutes or so), then remove the pan from the heat. Keep the sauce warm while you prepare the crabs.
Wash the crabs and remove the dead man's fingers (the gills) from underneath the shell, and cut off the eyes and mouthparts.
Heat the vegetable oil in a large heavy kettle to 375 degrees.
Blend salt and pepper into flour, and coat each crab lightly with flour.
Place a crab top side down on the end of a long-handled kitchen fork (do not skewer it), with the legs and claws hanging down.
Carefully lower all but the body into the hot oil. Hold that position for about fifteen seconds, and then carefully flip the crab backwards into the oil. Fry two at a time until golden brown, and drain. (Let the heat of the oil recover before frying the second batch.) Keep warm.
Reheat the sauce and add the pecans. Stir the pecans in and cook for about two minutes, then serve over the crabs.