Step 1
Start from a dress block with zero to very small wearing ease (2 to 4cm at each circumference, according to the fit you prefer) and trace front and back separate.
Lengthen to ankles, then on front draw underbust line and a parallel line 6 to 8cm below it: these two lines identify the width of underbust band. We suggest underbust band to sit few cm (2 to 3cm) above waistline.
Draw a line matching to bottom one also on back.