01 - Pat the beef chuck roast completely dry with paper towels. Season generously with salt and freshly ground black pepper on all sides.
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 - Place the sliced yellow onions, carrot pieces, and halved baby potatoes in an even layer at the bottom of a 6-quart or larger slow cooker insert.
04 - Position the seasoned beef chuck roast directly on top of the vegetable bed. Pour the prepared Korean marinade evenly over the meat and vegetables, ensuring all surfaces are coated.
05 - Cover the slow cooker with its lid. Cook on LOW setting for 8 hours until the beef pulls apart easily with a fork and reaches internal temperature of 205°F.
06 - Carefully remove the beef roast and vegetables from the slow cooker using tongs. Arrange on a large serving platter and cover loosely with foil to retain heat.
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 - Whisk together cornstarch and water in a small bowl until smooth. Gradually 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 - Using two forks, shred the beef chuck roast into bite-sized pieces. Arrange the shredded beef alongside the tender vegetables. Spoon the hot soy garlic gravy generously over the entire dish.
10 - Scatter the thinly sliced scallions and toasted sesame seeds over the top as a finishing touch. Serve immediately while hot.