In a glass measure, whisk together olive oil, vinegar, ginger, garlic, salt, cinnamon, coriander, paprika, sugar, cumin, pepper, and cayenne.
Rinse flank steak and pat dry; put in a 1-gallon zip-lock plastic bag.
Pour in all but about 3/4 cup of the marinade (save remaining for grilled eggplant and pepper salad - recipe#200475) seal bag and turn to coat meat well.
Chill for at least 4 hours and up to 1 day.
Lift steak from marinade (discard used marinade) and lay on a well-oiled grill over a solid bed of medium-hot coals or medium-high heat on gas grill; close lid on gas grill.
Cook steak, turning occasionally, until browned on both sides and still pink in the center (medium-rare, cut to test) 10 to 12 minutes total.
Transfer steak to a platter or rimmed board and let rest 5 minutes.
Then cut across the grain into thin, slanted slices.