What should I do if the tray on the dining table is unstable?

Pro suggests that you take a brick to practice, and then add another brick to yourself after practice. In the process of practice, you use the tray with your left hand, put your right hand behind your back, spread your fingers with your left hand, open it like a fan, stand up straight, hold your chest out, and look ahead, not at the tray. Your steps must be natural, not fast or slow. Keep your left hand balanced when you bend over, and don't shake it. And don't look at the tray, just look at what you want. Practice repeatedly like this, and it will be fine naturally.