01 - Pat the beef chuck roast thoroughly dry with paper towels. Season all sides generously with salt and freshly ground black pepper.
02 - In a medium mixing bowl, whisk together soy sauce, beef broth, brown sugar, sesame oil, minced garlic, grated ginger, rice vinegar, and gochujang until the sugar dissolves completely.
03 - Arrange the sliced onions, carrot pieces, and halved baby potatoes in an even layer at the bottom of a 6-quart or larger slow cooker.
04 - Place the seasoned beef roast directly on top of the vegetable bed. Pour the prepared marinade over the beef and vegetables, ensuring even coverage.
05 - Cover the slow cooker with its lid. Cook on LOW setting for 8 hours until the beef shreds easily with a fork and vegetables are tender.
06 - Carefully remove the beef roast and vegetables from the slow cooker using tongs. Transfer to a large serving platter and cover loosely with foil to keep warm.
07 - Pour the cooking liquid from the slow cooker into a medium saucepan. Bring to a gentle simmer over medium heat, skimming any excess fat from the surface.
08 - In a small bowl, mix cornstarch and water to form a smooth slurry. Whisk the slurry into the simmering liquid. Continue cooking for 2-3 minutes, stirring constantly, until the gravy thickens and coats the back of a spoon.
09 - Shred the beef using two forks or meat claws. Arrange the shredded beef and vegetables on plates. Drizzle generously with the warm soy garlic gravy.
10 - Sprinkle with thinly sliced scallions and toasted sesame seeds immediately before serving.