Soak wooden skewers in water for 20 minutes to prevent them from burning on the grill.
Cut the pork belly and pork tenderloin into uniform 1-inch cubes for even cooking.
In a small mixing bowl, whisk together the gochujang paste, sesame oil, tamari, honey, minced fresh ginger, and minced garlic.
Place the pork cubes in a bowl and toss with half of the prepared gochujang marinade until well coated.
Slice the red bell pepper and zucchini into 1-inch pieces suitable for skewering.
Thread the marinated pork and vegetables onto the skewers, alternating the pork belly with the leaner tenderloin and the vegetables.
Season the assembled skewers lightly with sea salt and black pepper on all sides.
Preheat a grill or grill pan to medium-high heat and lightly oil the grates with a high-smoke-point oil.
Grill the skewers for 4 to 5 minutes per side, turning occasionally, until the pork is cooked through and has a nice char.
Brush the remaining marinade onto the skewers during the final 2 minutes of grilling to create a sticky glaze.
Remove from the heat and garnish with sesame seeds and thinly sliced green onion before serving.