Add the beef to the slow cooker, followed by the soy sauce, brown sugar, beef broth, sesame oil, garlic, ginger, rice vinegar, and red pepper flakes.
Cover and cook on low for 8–9 hours or high for 4–5 hours, until the beef is fall-apart tender.
Remove about ¼ to ⅓ cup of the cooking liquid and whisk in the cornstarch until completely smooth.
Pour it back into the slow cooker, cover, and cook on high for another 20–30 minutes.
Serve over jasmine rice with green onions, sesame seeds, and something green.
Add chili crisp if you like a little heat.
