Nestle the duck in a flameproof baking dish, preferably on a wire rack, that will comfortably hold the duck with some space around it, breast side up, and refrigerate, uncovered, until the skin and its coating are completely dry, about 48 hours. Check the duck after 24 hours, and if any liquid has accumulated in the bottom of the dish, drain it off and discard it, and then return the duck to the fridge.