Slice the pork belly and pork tenderloin into uniform 1-inch cubes.
In a small bowl, whisk together the gochujang, sesame oil, coconut aminos, rice vinegar, minced ginger, and minced garlic to create the marinade.
Place the pork cubes in a glass bowl and toss with the marinade, allowing it to sit for at least 20 minutes in the refrigerator.
While the pork marinates, chop the red bell pepper and red onion into 1-inch pieces suitable for skewering.
Thread the marinated pork and vegetables onto skewers, alternating between the pork belly, tenderloin, pepper, and onion.
Season the assembled skewers lightly with sea salt and black pepper.
Preheat a grill or grill pan to medium-high heat and cook the skewers for 10-12 minutes, turning every few minutes until the pork is cooked through and the edges are caramelized.
Remove from the heat and garnish with thinly sliced green onions and sesame seeds before serving.