Place the pork belly cubes into a large prep bowl and drizzle it with olive oil. Mix it to spread it evenly, then add the spice rub. Use your hands (in food-grade gloves) to distribute it over all of the pork belly.
Fill your smoker with hickory or applewood pellets and preheat it to 250ºF. Place the pork on the smoker grill grates and smoke until the internal temperature of the meat is 165-170ºF (about 2-3 hours).
Place the covered meat tray on the smoker and cook at 250ºF until the internal temperature of the meat is about 200ºF (about 1 1/2 hours). Then remove the foil and smoke for another 15 minutes to thicken the sauce. Remove the tray and let the Pork Belly Burnt Ends rest for 15 minutes. Serve.