Prepare a leg of lamb for roasting by trimming the shank bone and the fat, making slashes in the meat with a knife and applying a rub made of spices and oil. Next, let the lamb sit out for about a half hour for the flavors to sink in.
To prepare a leg of lamb for roasting, first trim the extra flesh off the shank bone using a paring knife. Some legs of lamb also have tough outer layers of fat known as fell. Trim this off thoroughly using a long, thin and very sharp knife. After removing the fell, trim the rest of the fat from the leg using shears to cut the fat pads around the hip area.
After trimming the fat, use a knife to make incisions in the meat 1 inch long and 1/2 inch deep to allow the spice rub to penetrate more easily. A good spice rub for leg of lamb consists of salt, pepper, rosemary and garlic. Mix these with oil and mustard until a wet paste forms, and then slather this evenly onto the leg, making sure to rub it into the slashes. After applying the spice rub, let the lamb sit out at room temperature for 30 minutes before baking in the oven.