Soak wooden skewers in water for at least 20 minutes to prevent them from burning on the grill.
Cut the pork tenderloin and pork belly into uniform 1-inch cubes to ensure even cooking.
In a small mixing bowl, whisk together the gochujang, coconut aminos, toasted sesame oil, rice vinegar, grated ginger, and minced garlic.
Place the pork cubes in a glass bowl and coat thoroughly with the marinade, allowing them to rest for 15 minutes to absorb the flavors.
Cut the red bell pepper into 1-inch squares and the green onions into 1-inch pieces.
Thread the marinated pork and vegetables onto the skewers, alternating between the lean pork, rich pork belly, and vegetables.
Heat a grill or grill pan over medium-high heat until hot.
Grill the skewers for 10-12 minutes, turning every few minutes, until the pork is cooked through and the glaze is sticky and browned.
Remove from heat and season with sea salt and black pepper before serving hot.