Shav Aasan or corpse is an excelent posture to relax body. It can be done before starting yoga or at the end of yoga.

How to do it:
lie down
close your eyes
keep 2 feel distance on legs
tun palms upward to sky
relax and bring your attention to your breath.

Intially if you need help, put one hand on stomach and one hand on chest to feel the breath. When you are relaxed and aware of breath, bring the hands back to ground.

At this point you can do
body scan: bring attention to top of you head and slowly move down to each part of the body thanking/relaxing it.
OR
simply stay lying down and relax enjoying the bliss feeling of deep relaxation.

To end:
bring your attention back to body, slightly move fingers and feet
slowly turn to one side, put hands below your head.
slowly come into sitting posture
put hands together in prayer posture (Namaste)
and bow to your divine self.

(video to follow)