Lay the leg on the cutting board with its outer surface down, with the femur end towards your left and the shank end towards your right. Support the meat with your left hand. Using a sharp knife held in your right hand, make a slit-like cut directly over the femur down the entire length. Insert the tip of the knife under one side of the muscle flap created by your slit and gradually work your blade down the entire length of the flap to loosen it from the bone.
What you’ll need
Once the flap is loosened, run the knife around the bone more deeply two or three times to free most of the first side from the bone, then proceeding in the same manner with the flap on the other side. Once you have worked entirely around the bone, first from one side, then from the other. Most of the meat should be freed from the bone. Then work in a similar manner to separate the meat from around the knee.
A loose piece of cartilage, the kneecap, may come off with the meat. If this happens, then simply cut it out from the meat around it. Once the knee is free, continue to cut the remainder of the meat from the femur. Finally, cut the meat from the shank bone. It should come off quite easily. Discard the bones or save to make stock.
Cooking flat lamb
The meat from one side of the bone will be thicker than the meat from the outside. If you want to cook the lamb flat, lay the boned leg, outer side down, on the cutting board with the thicker muscle to your left. Hold it down with your left hand. Using a sharp knife in your right hand, hold the blade parallel to your cutting board.
Boning the bone of lamb
Make a single cut, moving from right to leave, parting through the thicker part of the meat so it can be unfolded to the thickness of the rest of the meat. To roll and tie the meat into a roast, form the meat into a cylindrical shape on the cutting board, and then tightly tie it with twine leaving gaps, each about an inch long.