Take the correct posture of Ukulele:
Holding the piano with the right upper arm, the inner side of the forearm and the right side of the chest, the flexibility of the elbow joint and the wrist joint is maintained. The flexibility of the wrist joint is very important when playing, especially when playing the rhythm.
When you are a beginner, you feel that it is difficult to stabilize the body. If you clamp it, you will feel that the elbow joint and wrist joint are not flexible. You need to practice and adapt more. Hold the corresponding position on the left hand and the thumb to the rear of the corresponding position. You can stand and hold the piano or sit and hold the piano in the same way.
When you sit, you can lift your legs and put the piano on your legs so that it can be more stable. Ukulele is small enough to be worn without a strap. Some pianos also have no connection to the straps. If you feel that the piano is unstable, you can make a small strap yourself.