This is so simple I'm embarrassed. Anyway, lately I've been cooking duck legs in a slow oven (250 degrees) for three hours. I rub the legs with a mixture of salt and toasted Sichuan pepper a day before cooking and leave them in the fridge. During roasting the fat all melts away, leaving only a lovely crunchy skin structure and very succulent meat.
I trim all the excess skin and fat from the legs and grind it with some beef chuck to make delicious hamburgers.