Preheat the oven to 400°F
Pat the boneless leg of lamb dry
Trim excess fat if needed
Season all over with salt and black pepper
Rub with olive oil
Add minced garlic, rosemary, and thyme
Tie the lamb with kitchen twine if needed for even cooking
Place the lamb in a roasting pan or oven-safe skillet
Roast for 15 minutes at 400°F
Reduce the oven temperature to 350°F
Continue roasting until the internal temperature reaches 135°F for medium-rare or 145°F for medium
Remove from the oven and tent loosely with foil
Rest for 15 to 20 minutes
Slice against the grain
Serve immediately