Hold the cooked leg by the shank bone with your left hand. Hold the leg, knee down, on the cutting board. Use a sharp knife in your right hand to cut thin slices from the muscle above the bone. Start at the hip end and work towards the shank, slicing at about a 45o angle to the bone. After each slice, rotate the knife blade and make a slice towards your left, to separate the slice from the leg.
When all the meat has been cut from the back of the leg, flip it over and slice the meat from the meat side in a similar manner.