Heat the oil in a large, heavy pan and add the flour.
Cook, stirring, to make a medium-brown roux (the color of peanut butter).
Add the onion, scallions, garlic and celery and cook until softened.
Add the tomatoes with their juice, breaking them down with the side of a spoon, then add the tomato paste, parsley, thyme, bay leaf, allspice, cloves, salt, peppers, cayenne to taste, lemon juice and water.
Bring to a boil, stirring well.
Add half the crabmeat and the whole crabs or claws.
Simmer for 1-1/2 to 2 hours, stirring occasionally.
If you like, you can scoop out allspice, cloves and bay leaf.
Add the shrimp and the remaining crab and simmer for a further 15 minutes.
Remove the pan from the heat and stir in enough file powder to thicken.
Do not boil the gumbo after adding the file powder.
NOTE*****Other seafood, such as purged crawfish, lobster and well scrubbed clams may be added to the gumbo, as available.
Cooked seafood may be used, too.
The finished gumbo will not have the richness of flavor given by crab cooked in it, but will still be delicious.
Just heat cooked seafood through in the finished sauce.