You sew a circle with a diameter of 10 cm in the middle of the handkerchief. The height of this circle is 1 cm, and then you can turn. This is a flat circle. If you need to turn the vertical circle, you need to practice. You can hold the edge of the handkerchief with your mother finger, forefinger and middle finger and swing it obliquely from the inside out. After many exercises, you can turn.
You try to practice. Wish you success!