How to Make It
Place the flour and beef in a large ziplock plastic freezer bag; seal and shake to coat. Heat the oil in a large nonstick skillet over medium-high. Add half of the beef to the skillet, and cook, stirring occasionally, until browned on all sides, about 6 minutes. Transfer the beef to a 5- to 6-quart slow cooker coated with cooking spray, reserving the drippings in the skillet. Repeat the procedure with the remaining beef. Add the garlic to the reserved drippings in the skillet, and cook, stirring occasionally, until fragrant, about 1 minute. Add the garlic to the slow cooker.
Stir together the vinegar, sesame seeds, soy sauce, brown sugar, Sriracha, ginger, and salt in a small bowl, and pour over the beef in the slow cooker. Cover and cook on LOW until the beef is very tender, 8 to 9 hours.
Remove the beef from the slow cooker, reserving the cooking liquid. Pour the cooking liquid through a fine wire-mesh strainer into a bowl, discarding the solids. Divide the beef among the cabbage leaves; sprinkle with the scallions, and drizzle each serving with 1/4 cup of the cooking liquid.