Step 1Wash and dry the pork belly. Place the pork belly in a large, sealable plastic bag.
Step 2In a small bowl, combine the salt, maple syrup, mustard seed, bourbon and several grinds of black pepper to form a marinade.
Step 3Pour the marinade in the bag, massaging it into the pork belly. Seal the plastic bag, pressing out all of the air.
Step 4Refrigerate the pork belly for 3 days, turning it once every day.
Step 5Remove the pork belly from the marinade, wiping off any excess and cut it in half.
Step 6Prepare the smoker: Spread about 3 tablespoons wood chips in the center of the base of the smoker, directly over the burner. Place the drip pan (if using) over the chips, and a rack on top of the drip pan. Place the pork belly in the center of the rack. Place the lid on the smoker, leaving about 2 inches uncovered.
Step 7Place the smoker over medium heat just until the chips begin to smoke. Cover the smoker entirely with the lid and reduce the heat to medium-low. Continue to gently smoke the pork belly until a thermometer inserted in the center reaches at least 150 degrees, about 1 hour. Remove from heat and uncover the smoker.
Step 8The pork belly is fully cooked. Slice the pork belly and serve immediately, or cool to room temperature, then cover tightly and refrigerate (or freeze) until needed. The pork belly will keep for 3 to 5 days, refrigerated, or up to 3 months frozen.