Lie down in such a way that
How do you do that?
You prop your shoulders and back of the head up until your achieve the above.
In terms of alignment:
The amount of bolstering you will need under your shoulders and head will vary. You may need very little or you may need a lot.
The more you work on relaxing your ribcage and your pelvis and releasing tension in your shoulders and neck, legs and hips the closer you will get to the floor!