Preheat the oven to 200 degrees F (95 degrees C).

Lay a large sheet of aluminum foil on a flat work surface. Lay 1/2 of the green parts of the green onions down in the center of the foil. Place pork belly, fattiest-side down, on top of the green onions. Top with remaining green parts of the green onions and sprinkle with salt. Fold aluminum foil tightly around pork and green onions. Wrap pork belly again in another sheet of aluminum foil. Place wrapped pork, seam-side up, into a loaf pan.

Cook pork belly in the preheated oven for 5 1/2 hours. Turn off the oven and let cool in the oven for 2 hours. Remove from the oven and chill in the refrigerator, 8 hours to overnight.

Remove pork from the foil and discard green onions. Cut pork into eight pieces.

Cook bacon in a skillet over medium heat until crisp all over, 2 to 4 minutes per side.

Whisk brown sugar, rice vinegar, fish sauce, ginger juice, and soy sauce together in a bowl.

Remove most of the fat from the bacon skillet and discard. Add 1 tablespoon of the brown sugar glaze and increase the heat to medium-high. Add pork and cook until caramelized and glazed on all sides, about 10 minutes. Make a well in the center of the skillet and add white parts of the green onion, garlic, and peppers. Sauté until fragrant, about 1 minute.

Pour water and remaining brown sugar glaze into the skillet; simmer until sauce thickens, 3 to 5 minutes.