In a bowl, whisk together olive oil, soy sauce, red wine vinegar, honey, garlic, black pepper, salt, and red pepper flakes.
Place the flank steak in a resealable plastic bag and pour the marinade over it. Seal the bag and refrigerate for at least 2 hours, or overnight for best results.
Preheat the grill to medium-high heat.
Remove the steak from the marinade and discard the marinade.
Grill the flank steak for about 5-7 minutes on each side for medium-rare, or until desired doneness.
Remove from the grill and let it rest for 10 minutes before slicing.
Slice against the grain and serve.