Setting up:
Get yourself a bunch of blankets or pillows and stack them up neatly into a lengthwise pile. As long as your props are of a length equal to or greater than your torso, you are set.
Coming into the pose:
Sit on your shins on the floor with a bolster (or pillow pile) at your side (next to one thigh). The bolster should extend long-ways away from the body. Let your seat slide off of your legs towards your bolster / pillows so that you are seated with your knees bent and your feet are slightly away from your body, off to one side.
Turn the torso so the belly is facing the bolster, place one hand on either side of the bolster, lengthen the spine, then start to lay the body down on the bolster for a side-reclining, supported twist. Head can rest facing either side. Arms can rest in a comfortable position.
For full support make sure that the bolster / blankets /pillows are right up against your thigh before you lay down. Height of your bolster is determined by length of torso. For example, a more petite person may only need 2 folded blankets or pillows, whereas a longer waisted person might need 3-4 folded blankets and possibly an extra one to raise their head.
Stay in this pose as long as it is comfortable for you. Try to take this pose on each side for about the same length of time.
Switching sides and/ or exiting the pose:
To come out or change sides, push the palms against the floor to gently raise the torso up off of the bolster, unwind slowly, and take a few breaths before switching sides or moving to a new pose. I like to swing my knees in front of me to come to the other side, but some of my students sit on their butt and swing their legs all the way around instead. Either way is fine.
Enjoy!