In a small baking bowl, combine salt, crushed peppercorns, scallions and ginger. Grate the spices with a large spoon or possibly between your hands to release the aroma. Later, rub the duck inside and out with the mixture, pressing the scallions and ginger firmly against the inside and outside skin to adhere. Cover with aluminum foil or possibly plastic wrap and place on a plate in the refrigerator for at least 6 hours or possibly overnight.
Before cooking, in a small baking bowl, mix the soy sauce well with the five-spice powder and coat the skin and inside of the duck with it.
Pour enough boiling water into the bottom of a steamer pot to reach 2 1/2 inches below the insert. Place the duck backside down on a deep, ovenproof plate that is an inch smaller in diameter than the cooking pot so that the steam can reach the duck unimpeded. Place the plate on the insert, cover the cooking pot tightly, and bring the water to a bubbling boil. While allowing the water to make continuously, steam the duck for 2 hours. You should always have a kettle of boiling hot water ready to replace any water that has boiled away.
Now turn off the heat, rest the duck in the tightly closed steaming pot for half an hour and turn it over to the other side on the breast side.
Close the cooking pot again and let the duck rest on the breast side for another 30 min.