Press down through your sit bones to sit up tall on the short box.
Both feet are flexed and under the footstrap.
Send length down the backs of your legs while thinking of pulling up the front and inner thigh.
Release one foot from the footstrap and allow a deep crease in your hip as you fold at the hip and knee to bring your knee up toward your chest. Your foot is softly pointed.
Hook your forearm behind your knee.
You will have rocked back slightly off your sit bones but your job is to engage your abdominal muscles and not slump back but scoop your abdominal muscle in and up, lengthening your spine in both directions.
Inhale to extend your leg toward the ceiling*. Exhale to bend the knee again.
Repeat that move 3 times.
Lengthen your spine each time you bend and stretch the leg.
*It is more important that you not give way too much in the spine and pelvis than it is to have a straight leg so bend your knee slightly if you need to.