Place the sliced flank steak in the bottom of the slow cooker.
In a mixing bowl, stir together the soy sauce, brown sugar, garlic, ginger, and beef broth until the sugar dissolves.
Pour the sauce over the beef and stir to coat all the slices.
Cover and cook on low for 5 hours until the beef is tender.
Stir the cornstarch slurry into the slow cooker, then cover and cook 20 minutes more until the sauce thickens.
While the sauce thickens, steam the broccoli florets until bright green and crisp-tender.
Spoon cooked rice into bowls, top with beef and sauce, then add steamed broccoli.
Finish each bowl with sliced green onions and sesame seeds.