Cut the pork shoulder into uniform 1-inch cubes to ensure even cooking and a consistent texture.
In a medium glass bowl, whisk together the gochujang, tamari, toasted sesame oil, grated ginger, minced garlic, rice vinegar, honey, and black pepper.
Add the pork cubes to the bowl and toss thoroughly until every piece is well-coated in the vibrant red marinade.
Cover and refrigerate for at least 30 minutes to allow the bold, spicy flavors to penetrate the meat.
If using wooden skewers, soak them in water for 20 minutes, then thread 4-5 pieces of pork onto each skewer.
Preheat a grill or cast-iron grill pan over medium-high heat and lightly grease with a high-smoke point oil.
Grill the skewers for 3-4 minutes per side, turning occasionally, until the pork is cooked through and the edges are beautifully charred.
Transfer the skewers to a serving plate and garnish with thinly sliced green onions for a fresh, crisp finish.