Preheat the oven to 500 degrees or as high as your oven goes.
Unwrap the duck, pull out any innards, set aside the liver for another use, and place the rest of the giblets in a pot covered with water to create a broth for the gravy.
Season the inside and out with Kosher salt. Stuff the onions & clementines inside the cavity. Puncture the layer of skin & fat lightly in a few places, but avoid breaking through to the flesh. Lay the duck on a wire rack in a roasting pan breast side down.
Reduce the oven to 400. Roast for 30 minutes. Flip over.
Place the thermometer in the meat if it is an oven safe tool. If not, check the temperature. Roast for 15 more minutes, until the skin starts becoming golden. Check the temperature again.
Reduce the heat to 300. Continue to roast 8-12 minutes per pound. The thighs will be done at about 150-155 degrees. The breasts internal temperature will be about 160-165.
If the thighs are not your desired ‘doneness’ you may have to cut them off and roast them separately for additional time, otherwise the breast will dry out.
Allow the duck to rest for 15 minutes and strain off the excess drippings & juices. Strain off the fat for another use. The remaining juices can be used in a gravy or sauce.