1. Fold down follow the dashed-line and spread out

2. Fold it follow the dashed-line on both sides to abut at the middle crinkle

3. Fold down for making the transverse crinkle and fold it follow the dashed-line to abut the transverse crinkle at the center

4. Spread the inner part out to be a trapezium shape

5. Fold the lower-part follow the dashed-line to abut at the center as the third step

6. Spread the inner part out as the fourth step and then fold follow the dashed-line

7. Finish