Prepare the marinade by whisking together olive oil, soy sauce, Worcestershire sauce, red wine vinegar, garlic, and black pepper in a small bowl.
Place flank steak in a gallon-sized sealable plastic bag and pour in marinade. Seal the bag and place it in the refrigerator for 4 hours, flipping the bag over at least once to ensure even coverage.
After four hours remove the steak from the marinade and discard the leftover marinade.
Optional but recommended: Let the steak come to room temperature and season steak with kosher salt.
Set your broiler to high heat and place your oven rack to its highest setting.
Lay the steak on a boiling pan, or use a cooling rack placed on a rimmed baking sheet and place under the broiler so it is just a few inches below the element
Broil steak with the oven door propped open for approximately 12 minutes to reach 135 degrees, or medium-rare. Remove the steak from the oven 10 degrees below your ideal doneness, as the temperature will continue to rise as it rests.*
Let the meat rest on your cutting board for 10 minutes.
Slice flank steak against the grain and serve.