01 - Pat the beef chuck roast thoroughly dry with paper towels. Lightly season both sides with salt and freshly ground black pepper.
02 - In a medium mixing bowl, whisk together the soy sauce, beef broth, brown sugar, sesame oil, minced garlic, grated ginger, rice vinegar, and gochujang until the sugar is completely dissolved.
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 chuck roast directly on top of the vegetable bed. Pour the prepared marinade evenly over the beef and vegetables, ensuring everything is well coated.
05 - Cover the slow cooker with its lid. Cook on LOW setting for 8 hours, or until the beef is fork-tender and easily shreds apart.
06 - Carefully transfer the cooked beef roast and vegetables to a large serving platter using tongs or a slotted spoon. 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.
08 - In a small bowl, mix the cornstarch and water together to form a smooth slurry. Whisk the slurry into the simmering liquid and continue cooking for 2 to 3 minutes, stirring constantly, until the gravy thickens to your desired consistency.
09 - Using two forks, shred the beef into bite-sized pieces. Arrange the shredded beef and vegetables on plates or a serving platter. Drizzle generously with the soy garlic gravy.
10 - Scatter the sliced scallions and toasted sesame seeds over the top of the dish just before serving.