Let’s draft the pattern of this blouse.
Start from a basic block with darts.
On front move the waist dart closer to the side.
Draw the collar line and draw the parallel to center front for the sheer part and the slash lines for the dart manipulation.
On the copy of your front draw the flounce as it should look in the finished garment.
Trace the flounce drawing it open:
a stiff fabric as a double organza is just perfect to hold that volume!
Your new pattern is ready: front, back, center front, collar, rouche.