Pat dry the pork belly and cut into 4 squares, slightly larger than a slice of bread.
Lightly slather the pork belly with mayo then liberally season with the BBQ rub.
Preheat your smoker to 275 degrees, then smoke the pork belly for 2-3 hours, until it reaches an internal temperature of 200-205 degrees and is probe tender.
Toast the bread slices and slather one side of each piece with mayo. Place sliced tomato, lettuce and a square or smoked pork belly on a slice of bread and top with remaining bread.
Optional toppings may include mustard, avocado, bacon, and pickled red onions.
Notes
Note: If pork belly is getting too dark before reaching tenderness, spritz with apple juice of a combination of apple juice and apple cider vinegar.