Pat duck legs very dry with paper towels. Using a sharp knife, lightly score the skin in a criss-cross pattern, being careful not to cut into the meat; this step helps the fat render and the skin crisp.
Sprinkle salt evenly over the skin and flesh of each leg, coating all sides. Let the duck rest, uncovered or loosely covered, in the fridge for at least 30 minutes (up to a few hours) to dry the skin slightly and enhance flavor.
Preheat your oven to about 300°F (150°C).
Place duck legs skin-side up in a snug, oven-safe dish. As they cook, the fat under the skin will render and partially surround the legs. Bake for 2–3 hours, or until the meat is very tender and easily pulls away from the bone.
To get extra-crispy skin, increase the oven temperature to 425°F (220°C) for the last 10–15 minutes, or switch to the broiler briefly, watching closely so the skin becomes deep golden and crisp but does not burn. Ensure the duck reaches at least about 165°F in the thickest part.
Let the duck rest for 5–10 minutes. Serve whole legs, or shred the meat off the bone and spoon the crispy bits and juices over salads and roasted vegetables.