Preheat the oven to 300.
Take the thawed duck, dry it well inside and out, put a chunk of onion, a couple pieces of celery and carrot, some thyme and some salt and pepper in the cavity.
With a fork or point of a knife, puncture the skin (and only the skin) all over, particularly in fatty areas.
Place the duck, breast up, on a rack inside a roasting pan and begin roasting.
After an hour, pull it out, drain off the rendered fat and reserve (duck fat is great for frying eggs and potatoes;  it costs like $8 to $10/lb, so you're making money buying a duck), find places on the skin you didn't puncture earlier and puncture them, then turn the duck breast down and return to the oven.  Leave it alone for an hour.

After the second hour, repeat what you did at the end of the first, turning it to rest on one side.

After the third hour, repeat what you did at the end of the first hour, turning the duck to rest on the other side.

By now, the house smells great.

After the fourth hour, repeat what you did after the first, turning the duck to rest breast up.

By now, the house smells better.

At the end, you should get about a pint of duck fat and glace and a roasted duck which will have loads of crispy skin and will fall apart in tenderness when you carve.

The aroma will be such that your knees buckle in pleasure.

If you want, you can glaze the duck.  
Mix a three or four or five consonant flavors into a glaze and paint it on the duck beginning at the end of hour two.

You can also make it Chinese style, by putting a knob of ginger in the cavity at the beginning and basing a glaze on soy and hoisin.  This makes great moo shu duck, BTW.