Place the cubes on the tray over a flat tray then add a layer of sweet rub on every side. Repeat with the savory rub. Rest until the BBQ is at temperature.
Set the barbecue (smoker or closed grill set at indirect heat for smoking) at 275 degrees F (135 degrees C).
Transfer the rack to the barbecue and cook for 2 hours. After this time the bark will be set.
Transfer the pork belly cubes to a tray and sprinkle with the brown sugar, honey, 1/3 cup BBQ sauce, butter, and ginger beer. Cover tightly with a sheet of foil.
Return the tray back to the barbecue and cook for another 2 hours.
Preheat the remaining sweet BBQ sauce for the glaze.
Remove the pork belly from the barbecue. Submerge in the preheated sweet BBQ sauce and return to the rack.
Place the rack of glazed pork belly burnt ends into the barbecue for 5 minutes to set.
Remove from the BBQ and let rest for 5 minutes (or cool not to burn your mouth) then serve.