This shape can be done via the usual cat shape, or seated by rounding the spine forward. (fivepillarsyoga.com)
Then, slightly lean back without rounding your spine — this part is particularly important (and hard), but don't let your spine curve or the exercise won't work. (businessinsider.com)
Hold for 5 breaths, keeping the breath smooth, and then rest the feet back down and round the spine as you hug your knees. (mindbodygreen.com)