Pat the flank steak dry
Trim any excess surface fat or silver skin
Season generously with salt and black pepper
Add optional marinade or dry rub if desired
Let the steak sit at room temperature for 20 to 30 minutes
Preheat the grill to high heat
Clean and oil the grill grates
Place the steak on the hottest part of the grill
Grill for 4 to 6 minutes on the first side
Flip once and grill for 3 to 5 minutes on the second side
Check for medium-rare doneness, about 130 to 135°F
Remove the steak from the grill
Rest the steak for 10 minutes
Slice thinly against the grain
Serve immediately