Preheat the oven to 300.* Rinse a 5-lb. duck inside and out; pat dry. Remove the excess fat from the neck and hind cavity and discard. Cut off the wing tips. Sprinkle the duck inside and out with kosher salt and pepper. Stuff the cavity with 3 chopped garlic cloves and a small bunch of fresh thyme. With a sharp paring knife, pierce the duck skin without cutting into the flesh, by inserting the tip of the knife on a sharp diagonal almost parallel to the bird; make dozens of slits all over the bird.
Place the duck breast-side-up on a rack set in a roasting pan. Roast the duck for 1 hour. Remove the bird from the oven and carefully pour off the fat into a measuring cup,** making sure to hold the bird and rack securely with a kitchen fork. Pierce the skin again and turn the bird over. Repeat this process every hour. After 4 hours, increase the oven temperature to 350. The bird, which should be breast side up at this point, should be golden brown. Season the skin liberally with salt and pepper and cook until the skin is browned and very crisp, about 1 hour longer. Remove from the oven and allow the duck to rest for 20 minutes.