1: Make the cure: Place the salt, sugar, pepper and Prague powder in a small bowl and mix well with your fingers.   Sprinkle half the cure on one side of the pork belly, rubbing it into the meat with the palm of your hand.   Invert the pork belly and rub the other side the same way. 

2: Place the rubbed pork belly with any extra cure in a large resealable plastic bag.   Cure on the bottom shelf of your refrigerator for 6 to 10 days, turning the bag over twice every day.   Liquid will release from the pork belly—it’s supposed to, as the rub becomes a brine.   Leave it in the bag. 

3: Drain the pork belly in a colander and rinse well.   Blot dry with paper towels. Let it dry until tacky on a wire rack in the refrigerator for 4 hours. 

4: Set up your smoker according to the manufacturer’s instructions and heat to 170 degrees. Place the wood chunks or chips on the coals or in your smoker box. Lay the cured pork belly on the grill grate and smoke for 3-1/2 to 4 hours, or until the internal temperature reaches 155 degrees. Let cool, then refrigerate. Slice into 1/4 inch slices and grill or pan-fry until crisp. Refrigerate or freeze the remainder.

5: Assemble the sandwiches: Lightly grill the bread over medium-high heat for 1 to 2 minutes per side. Set aside. Grill or pan-fry the bacon slices until crisp; drain on paper towels. For each sandwich, spread mayonnaise on two slices of bread (one side only). Spread the third slice of bread on both sides with mayonnaise. Lay lettuce leaves on the bottom slice against the mayo-slathered side. Top with sliced tomatoes and 3 slices of bacon. Lay the bread with mayo on both sides on top. Repeat the sequence with lettuce, tomatoes, and bacon. Top with a final slice of bread, mayo-side down. Repeat for the second sandwich. Slice in half with a serrated knife and serve immediately.