The lying-down procedure (which goes by a number of names in the Alexander Technique) is one of the most classical procedures of the Technique. You lie down on a firm surface, knees up, head supported by books so that the head is not pulled back but that the neck is encouraged to release and a lengthening of the spine is promoted. Generally, it would mean that the neck vertebrae are more or less aligned with the rest of the spine, allowing for the natural curves of the spine. The hands are placed comfortably so as to allow the shoulders to ease and widen. The position adopted is one which facilitates lengthening and widening, and it will vary in detail from individual to individual.
This position is beneficial in itself. The knees up position tends to diminish any muscular pull on your lower back. While lying down the intervertebral discs reabsorb fluid (which is why most people are 1–2 cm taller in the morning than in the evening).* The back and neck muscles are allowed a – for most people – much needed rest.
Lying down for 10–15 minutes a day is a beneficial practice. This is a first step.
* ‘Diurnal changes in the profile shape and range of motion of the back’ by P. Wing et al. in Spine 1992 Jul;17(7):761-6.
(Image from Voice Power by Michael McCallion (© Mouritz, 2012).)