Combine pork shoulder, wine, oil, vinegar, salt, chile flakes pepper, cloves, garlic, bay leaves, and onions in a large bowl. Toss well to coat pork. Cover the bowl tightly and refrigerate for 24 hours.
Bring Wolf grill to medium-high heat. Thread the pork cubes on 6 long metal skewers, leaving only a slight space between cubes. Discard any remaining marinade. Grill the kebabs, turning them occasionally, until cooked through, tender, and lightly charred on all sides, about 14 minutes.