Heat an oven to 375°F. Cut the orange into very thin slices. Trim the roots and last inch or so of green tops of the green onions and cut into 2-inch pieces. With the flat of a chef’s knife, smash the garlic and discard the papery skins, if you’re using garlic.
Tidy up the chicken thighs by trimming off any excess skin or bits of fat. Season them generously with salt, pepper, and the Aleppo pepper.
Spread a bit of olive of oil on a baking dish that will fit the chicken without crowding. Arrange the orange slices in a layer and then arrange the thighs on top, with room to breathe (they will brown nicer if they’re not too tight). Toss in the green onions, garlic if using, and rosemary or thyme.
Roast in the heated oven until the chicken is fully tender and the skin is browned and slightly crisp, about 45 minutes depending on the size of the thighs. If you’re using the olives, toss them in during last 10 mins or so just so they warm up and pick up some flavors.
Remove the baking dish from oven, tilt it, and spoon off any excess fat, though take care to keep the juices in the pan.
Serve the chicken with a mound of the oranges and green onions, which should be tender and nicely flavored by the chicken fat and juices.