01 - Set the oven to 300°F to prepare for slow roasting.
02 - Dry the duck thoroughly with paper towels, then prick the skin evenly using a sharp knife or fork, avoiding piercing the meat.
03 - Season the cavity and exterior of the duck with kosher salt and black pepper. Stuff the cavity with orange quarters, lemon quarters, thyme, rosemary, and smashed garlic cloves.
04 - Place the duck breast side up on a rack inside a roasting pan. Roast for 2 hours, basting intermittently with pan juices and draining excess fat as necessary.
05 - Combine orange juice, orange zest, honey, balsamic vinegar, and soy sauce in a small saucepan. Bring to a boil, then reduce to a simmer over medium heat until the mixture reduces by half and thickens slightly (about 12–15 minutes). Whisk in the butter and set aside.
06 - Raise oven temperature to 425°F. Brush the duck generously with the orange glaze, then roast for an additional 20–30 minutes, basting once or twice until the skin turns deep golden and crispy.
07 - Remove the duck from the oven and let it rest for 15 minutes before carving. Serve alongside any remaining glaze.