Right side up, mark all of the cutting and fold lines with a blue wash-away marker. Next, cut along the solid lines, and fold under 1/8" of the left placket raw edge and stitch.
On the wrong side of the fabric, press the fabric open along the fold lines.
Right side up, lap the right placket over the left placket.
This leaves a pleat all the way down the back of the gown. I like to complete the gown and button holes before I top stitch along the dots at the bottom of the placket