Salamba Sarvangasana.

Here is the sequence by point - each number corresponds to the number on the drawing below.

1 - Preparing props for salamba sarvangasana for beginners

• A wall
• The support for the shoulders (here in Germany, one takes plates of recycled foam about 7 cm height + a cover ..)
• a chair
• a belt

First, the belt is prepared, the buckle should be shoulder width 
The plates are installed at a distance from a forearm of the wall 
The chair is arranged so as to catch the feet with the arms extended when resting on the support.

2 - Distance Shoulders / Support

When lying down, the student uses his thumbs to place his shoulders at the proper distance from the edge of the support. The correct distance corresponds to the length of one inch.

3 - Assemble the basin

The pupil begins to raise the pelvis by using his feet on the wall

4 - Switch the legs on the chair

It is here that the partner (in gray on the sketches) intervenes. He places himself on the side and ensures the student by placing his hands on each side of his pelvis and helps him eventually to tilt his legs on the chair.

5 - Halasana on chair

The student finds himself in Halasana, which is when the partner helps him pass the belt around his arms.

6 - placement of partner before final position

The partner is behind the student and places one foot on the belt between the student's arms (on the belt portion that is glued to the support, not the top one, because crushing it would return the elbows One to the other) and DELICATELY placing the knee at the level of the sacrum of his pupil: this is to help the student to find the proper alignment of the trunk and not to move the weight towards the neck!

7 - Help the student to get to the final position

Here the partner places his hands on the student's upper thighs and helps him climb one leg after the other vertically guiding with a hand at the level of the tibia.

8 - The student has officially arrived in Salamba Sarvangasana.

via: Iyengar Yoga Notes.