Preheat the oven to 375°F (190°C).

In a bowl, mix garlic, rosemary, thyme, olive oil, salt, pepper, and lemon juice to create a marinade.

Rub the marinade all over the boneless leg of lamb, ensuring it is well coated. Let it marinate for at least 30 minutes at room temperature.

Place the marinated lamb in a roasting pan and insert a meat thermometer into the thickest part of the meat.

Roast in the preheated oven for about 1.5 hours, or until the internal temperature reaches 135°F (57°C) for medium-rare.

Remove the lamb from the oven and let it rest for 15 minutes before slicing.

Slice the lamb against the grain and serve with your choice of sides.