Preheat the oven to 425°F
Pat the London broil dry with paper towels
Season both sides with salt, pepper, and any desired spices
Place the meat on a rack in a roasting pan or on a foil-lined baking sheet
Let the meat sit at room temperature for 20 to 30 minutes
Roast for 10 to 15 minutes per side, depending on thickness and desired doneness
Check the internal temperature with a meat thermometer
Remove at 125°F to 130°F for rare
Remove at 135°F to 140°F for medium-rare
Remove at 145°F for medium
Transfer the meat to a cutting board
Let it rest for 10 to 15 minutes
Slice thinly against the grain
Serve immediately