Rinse and drain the rice. Add to boiling water  with salt. Stir and bring to a boil again. Cover the pan. Turn the heat to low. Steam for 20 minutes. Drain. Stir the flour into 4 tablespoons of melted butter in a saucepan. Once smooth, add milk, stirring continually. Add mustard and oregano. Stir and cook for 10 minutes or until thickened. Stir in the crab meat and pimientos. Combine with the cooked and drained rice. To cool, spread on a platter. Shape into 8 small, or 4 large croquettes. Preheat the oven to 375ºF. Butter a large shallow baking pan. Place the croquettes in the pan. Dribble the remaining 4 tablespoons of melted butter over croquettes. Bake for 30 minutes or until golden brown. Turn the croquettes once, using 2 large spoons. Makes 4 or more servings. Serve with Cheese Sauce or Mushroom Sauce To deep fry: Heat your fryer to 390ºF. Lower 2 or 3 croquettes at a time into the hot oil.  Fry for 2 to 3 minutes or until golden brown. Drain on thick paper towels.