Assess the possible mounting points on the table's locking mechanism in front of you. Depending on your plane seat design, bend the two metal pieces into Z shape and bend the last piece into a long J. The Z shaped metal piece should have an indention more than the thickness of your phone.
Find a secure slot/gap/crack on the table locking mechanism to install your phone mount. After attaching, make sure that the flexible pieces are stiff and does not fall of.The J shaped piece is meant to hold the top part of the phone. It may not be seen in the photo but I just wedged the end of the J-piece between the tight gap between the fabric and locking mechanism.