Step 1
Work on back first: trace a full copy, adjust length to 10cm below knee line, then reduce 2 to 3cm from hemline at side seam, blending to zero at hipline.
Draw a first line: it’s slanted downwards from right to left. On right side seam pick a point 5 to 7cm below waistline, then pick a point on left side seam that is 10 to 15cm below waistline and connect them.
Draw a second line, slightly curved: it’s approx 3cm below hipline on right side and at hipline or 1cm above it on left side.