In a blender, combine the garlic, rosemary, oregano, mustard, honey & vinegar and puree until the garlic is minced. With the machine on, gradually add the oil and blend until creamy. Season lightly with salt and pepper.
Score the surface of the steak (on one side) before cooking to help the absorption of the marinade. Run your knife diagonally across the surface of the steak, in a diamond pattern. Make the slices about ¼-inch deep, and space them roughly 1-inch apart.
Add the meat to a resealable bag and pour all but ¼ cup of the vinaigrette on top; turn the meat to coat with the remaining vinaigrette. Refrigerate and let marinade for at least 4 hours and up to 24 hours.
Remove the steak from the fridge at least 30 minutes prior to grilling.
Preheat the grill on high. (Oiling the grates is advised as the honey may stick).
Remove the steak from the vinaigrette marinade, letting the excess drip off. Season with salt and pepper. Grill the steak over medium-high heat, turning occasionally, until lightly charred and an instant-read thermometer inserted in the thickest part registers 125°F, approximately 8-12 minutes.
Transfer the steak to a carving board and let rest for at least 15 minutes. Thinly slice the meat against the grain.
Serve sliced flank steak on warm tortillas with, guacamole, pico de gallo, sautéed mushrooms, fresh vegetables, rice and beans, corn salad, limes, hot sauce or any other favourite toppings.