Stabilize one band around each shoulder and under the opposite foot. With your knees bent in close to your chest, push your legs out to a full extension.
Tips:
Maintain constant tension on the bands.
Loop the bands around your feet to raise the resistance.
Unite bands with a clip or twist them in the middle to minimize the friction against your legs.
Variations:
Stabilize one band under both feet and around both shoulders.
Lower band(s) from your shoulders down toward your lower back for a more vertical press.