Mash the garlic, ginger and spices to a paste in a mortar and pestle (or mince and mash with a large knife). Pat the steak dry and rub the spice mixture all over the steak. Marinate the steak, covered and chilled for at least 6 to 8 hours.
Prepare the grill. Drizzle the steak on both sides with vegetable oil. Grill the steak 5-8 minutes per side for medium rare. Transfer steak to a cutting board and tent with foil to keep warm. Slice the steak at a 45 degree angle against the grain into thin slices. Serve.