There are several different ways, and everyone from the region will tell you how they do it, which of course will be slightly different and obviously more delicious than how everyone does it 🙂 Typically it is roasted slowly upright on a stake (cordero Magallanes al palo), like in the photo above.
Another way to roast it is sideways on a stake, cutting the lamb into 4 pieces. We prepare lamb sideways because we have accesses to this type of heavy metal stake that is necessary to hang the meat on.
The trick to slow roasting is in the fire and charcoal. It is important to keep a fire constantly burning, and scatter the hot coals underneath the lamb while always keeping the fire separate to produce more charcoal.
The flavor of the lamb comes from salt and a combination of onion, garlic, cilantro, aji, vinegar, water and whatever else you choose to add, combined into a liquid sauce which is basted on the lamb so as to not dry out. As it cooks, these flavors integrate themselves into the crunchy skin and meat, mmmm.
After 4-5 hours of roasting, listo! A feast of Magallanes lamb ready for whatever event.