Body Cues:
The front of the hip (anterior to the joint) now touches the bed, rather than resting on the hip joint.
Pillow(s) under the top leg (and also supporting the belly, if desired) should enable the pelvis and lower spinal area to feel squared up, supported, and aligned, with no pressure or pinching points.
The lower arm now contacts the bed in the chest space anterior to the shoulder joint, no longer resting on the shoulder joint but instead in the pectoral/ ribcage area. (Put your arm behind you.) The shoulder joint opens naturally in this position to allow the arm to rest just posteriorly to the torso.

A comfortable cervical pillow will likely be a smaller size than previously accustomed to. Look for the proper pillow to support the neck squarely and avoid jaw and esophageal pressure.
The lower arm should rest comfortably straight along your posterior side (as in pic) and this can be comfortably modified by tucking the forearm under your waist (elbow at 90˚ and palm of hand touching belly- no pic).
The neck and upper spine, lung space, and shoulder joints, should feel comfortably supported, square, and open. It is possible to breathe more deeply and comfortably in this position.

images: Stephen Marwood, 1996: The Alexander Technique Manual; Take Control of your Posture and Your Life
by author Richard Brennan