Turn duck upside-down and prick through the skin into the fat all over the bottom of the duck so the fat will drain. Preheat oven to 180ºC . Bake the duck in a little water around 30 minutes. (Grab a leg; if it moves, it is tender enough.) Keep duck covered with foil, but baste often.
Make the glaze of equal parts marmalade and orange juice concentrate, thawed. Can add a little sugar to make it stick better; glaze is prettier if you add about 1 tb. cornstarch dissolved in a little water.