Once you are confident generating and maintaining tension with bent knees. We can advance by straightening our legs - beginning with an upward angle.
Begin with knees bent, arms extended forwards, shoulders and upper back raised off the floor. Press your lower back into the floor and reach forwards, create tension through the whole body.
Now extend the legs and reach your arms overhead. Point your toes, maintain full body tension, control your breathing and hold for time.
Rest anytime your form breaks down, and reset, there is no point increasing your hold time with poor form.