The first time I worked in a western restaurant, they asked me to serve food on a tray, but when I served drinks, I was particularly nervous because I carried two drinks and then served them.
This is very simple. The stress point of the tray is not the palm. Remember, it's not the palm, but the higher place behind the five fingers and thumb. Don't touch the tray with your palm, and open your fingers as far as possible. So that the tray is not easy to turn over. Also, the tray can be dragged forward and can be used as a fulcrum near the arm, which is more stable!