Trace back and front separate, highlight underbust line, then mirror front to have it full.

Then:

• flare 12 to 18cm in center back, blending to zero at hips
• flare 8 to 12cm on front and back side seams, blending to zero at waist
• make sure front waist darts are 3cm wide at underbust and shaped as ‘rockets’

Now draw back neckline and shoulder strap:

• in center back, drop 2 to 3cm from waist and starting at right angle from cb draw a curve
• curve intersects waistline approx at waist dart
• close upper part of waist dart in a temporary way and continue the curve in direction of the shoulder
• shoulder strap is 3 to 4cm wide – you can draw it plain as shown in this image or you can discard 1cm from shoulder tip and then measure 3 to 4cm strap (in this second version, straps sits a bit closer to your neck and you have to redraw armhole a bit inwards).