Place your potjie directly over hot coals. Add a thin layer of high-smoke point oil. Working in small batches to avoid crowding, sear the oxtail pieces until a deep, dark brown crust forms on all sides. This crust (the Maillard reaction) is where the deep, savory umami flavors of the 'best oxtail potjie ever' are born. Do not rush this step; remove the meat and set it aside once perfectly browned.