Add 2 cups water to the pan and seal tightly with aluminum foil. Transfer to the oven and cook for 6 hours. When done, shred the pork with tongs.
For the crackle: Preheat the oven to 400 degrees F. Lightly salt the pork skin on both sides and set on a baking sheet. Transfer to the oven and roast, skin-side-up, until golden brown and crispy on both sides, 40 minutes to 1 hour. For even cooking, flip the pork skin every 15 minutes and drain some of the rendered fat while you do; the skin will render a whole lot of fat.
For the bacon jam: Place the bacon in a large skillet over medium-high heat and cook for about 10 minutes to render some fat and lightly brown the meat.
In a separate skillet, cook the onions over medium heat until they begin to soften, 5 minutes. Stir in the soy sauce and brown sugar.
Drain the fat from the bacon pan, then pour the onion-soy sauce mixture over the bacon. Cook over very low heat for about 2 hours, stirring occasionally. When the bacon has become darkly caramelized, turn off the heat and leave it to cool for an hour. When cool, transfer the bacon to a food processor and process until smooth. If you like your bacon jam really smooth, add a little water and some more brown sugar.
To assemble: Spread both halves of a bun generously with bacon jam. Add a healthy amount of pulled pork, then sprinkle crackle on the meat. Put the sandwich together and lightly grill it in a buttered pan or a flattop grill. Eat.