Diagonal is worked flat, from back to front. A neckline opening is created by parting the sts in two portions, then working them simultaneously while increasing and decreasing sts.
The sides are then grafted together, incorporating the pleats on the left side of the body.
This garment is intended to be worn with approximately 4 inches / 10 cm of positive ease, in order for the pleats to come out nicely - so choose your size accordingly.
corresponding to (actual garment measurement):
The last photo shows the calculated yardage needed per size.
Please note that gauge is not crucial for this project, as you will be working by measurements only. It is however recommended to work at a loose gauge, in order for the fabric to drape nicely.