Pat the flank steak dry with paper towels
Season both sides with salt, pepper, and any desired spices
Let the steak sit at room temperature for 20 to 30 minutes
Heat a heavy skillet or cast-iron pan over medium-high to high heat
Add a small amount of oil with a high smoke point
Place the steak in the hot pan
Cook for 4 to 6 minutes on the first side
Flip the steak and cook for 3 to 5 minutes on the second side
Use tongs to sear the edges for 30 to 60 seconds if needed
Check for doneness with a meat thermometer
Remove the steak at 130 to 135 F for medium-rare or 140 to 145 F for medium
Transfer the steak to a cutting board
Let it rest for 10 minutes
Slice thinly against the grain
Serve immediately