Let’s see how to draft the pattern of this wide neckline dress with wide sleeves.
Start from a basic dress with waist darts and kimono/dolman sleeve.
On back and front draw the new neckline and the slash lines on the sleeve.
On back, discard the dart from the center.
On front, draw the slanted line for manipulating the dart.
Separate skirts and bodices.
Cut through the slash lines and spread the sleeve pieces.
Manipulate the front bodice dart into the slanted pleat.
Redraw front and back bodices marking the sleeve pleats.
You should get: back bodice, front bodice, back skirt, front skirt.