Fill a large pot with water and bring to a boil. Add pork belly; cook until starting to soften, about 5 minutes. Drain.
Heat vegetable oil and brown sugar in a wok or large skillet over medium heat until sugar is melted. Add pork; cook until browned on all sides, about 2 minutes. Add dark soy sauce; cook and stir until flavors combine, about 5 minutes.
Transfer pork mixture to a slow cooker. Add rice wine, light soy sauce, scallions, ginger, and star anise. Pour in enough water to just cover the pork.
Cook on Low until pork is tender, about 6 hours. Add diced chicken substitute, hard-boiled eggs, and more water to cover.
Cook on Low until eggs absorb cooking liquid, rotating halfway through, about 1 hour more.
