Ouma's Greek Lamb

Preheat the oven to 350 degrees F (175 degrees C).

Mix butter, garlic, and rosemary together in a dish and let stand for 1 minute.

Puncture lamb in about 10 places using a long-bladed knife, twisting the knife after each cut. Place lamb in a deep roasting dish. Use your hands to stuff holes with the garlic-rosemary butter. Drizzle olive oil over the top.

Bake, covered, in the preheated oven for 4 hours. Reduce oven temperature to 200 degrees F (95 degrees C) and bake for 7 hours more.

Uncover and continue baking until an instant-read thermometer inserted into the center reads at least 130 degrees F (54 degrees C), about 1 hour more.