Sit on the floor with knees bent up in front of you and a piece of exercise band under your feet and holding each end with your hands. Find pelvic neutral by sitting up as straight as you can and then relaxing your pelvis down slightly. Widen at the collar bones to find thoracic neutral and lengthen in your neck as if you are holding a ripe peach under your chin. Engage pelvic floor and deep transverse abdominals and shoulder blades.
Holding the exercise band taut enough that it supports your weight, roll back off your sitting bones to flex your low back. Keep your stabilising muscles engaged. Turn your trunk towards the right as if you are turning the handle bars of a bike. Turn back to the middle and then turn to the left. Turn back to the middle.
Now roll forwards, maintaining a C shape of your spine and then roll back on to your sitting bones and in to pelvic neutral, again re-stacking your vertebrae, one on top of the other from tail upwards.
Only go as far as you feel comfortable and safe.