01 - Whisk together soy sauce, brown sugar, water, rice vinegar, sesame oil, ginger, garlic, gochujang, and toasted sesame seeds in a medium bowl until smooth and fully combined.
02 - Place beef chunks in the slow cooker and pour sauce over the meat, turning pieces to ensure even coating on all sides.
03 - Scatter half of the sliced green onions over the beef and sauce mixture.
04 - Cover and cook on low setting for 7 hours until beef is very tender and easily shreds with a fork.
05 - Shred beef directly in the slow cooker using two forks, then stir thoroughly to coat shredded meat with the sauce.
06 - Serve hot over steamed rice, in lettuce wraps, or with steamed vegetables. Garnish with remaining green onions, sesame seeds, and optional sliced red chili.