Chill the flank steak in the freezer for 20 minutes to make slicing easier.
In a mixing bowl, combine coriander, brown sugar, soy sauce, lime juice, minced garlic, and ground ginger. Whisk until the marinade is well mixed.
After removing the steak from the freezer, slice it thinly against the grain. Transfer the slices to a large mixing bowl and pour the marinade over them. Toss to ensure all pieces are well coated. Cover and let marinate at room temperature for an hour.
Position the oven rack about 6 inches from the broiler and preheat it. Line the bottom of a broiler pan with aluminum foil for easy cleanup.
Arrange the marinated steak slices in a single layer on the broiler pan's rack.
Broil the steak for 1 to 2 minutes, brushing with marinade occasionally, until it reaches your preferred level of doneness, aiming for medium rare.
