Clasp your foot behind your body with opposite hand
Pull your foot upwards, and push the knee backward
Contract your abdominals to stabilize the pelvis (do not arch your back).
Press the front hip bone forward and slightly extend the hip
Hold the stretch
Repeat for each leg
Notes
This stretch may be difficult to perform without holding onto something for support. If there is nothing available, one of the other quadriceps stretches may be more appropriate.