About 30 minutes before the lamb is ready to be cooked, preheat the smoker or oven to 225°. Next, mix the oil with thyme, rosemary, parsley, 5 roasted garlic cloves, salt, and pepper until combined.
Remove the lamb and place it fat side down on the rack. Using a sharp knife, make 1” wide and deep incisions in 20-25 places about ½” to 1” inch apart from each other.
Stuff a roasted garlic clove in each slit until all the holes are filled. Next, pour about a 1/3 of the herb oil mixture over the inside of the lamb and spread it out using a spoon or brush.