Let’s draft the pattern of this trendy shirt.
Start from a basic block with darts.
Draw the strapless neckline on both front and back, widen the shoulder dart by 1cm at front to make the neckline tighter.
Shape the underbust dart.
Onto the sleeve, draw the slash lines that you see to remove the upper part and to open some volume at the center/elbow area.
Put the upper part of the sleeve beside the front bodice matching the armhole and draw the neckline band.
Get the sleeve pieces, separate them as you see in the photo and redraw the two parts of the sleeve with the added volume.
Trace the three separate copies for the bodice (back with closed dart, center front, side front panel) and cut some slash lines through the front ruffle to add the gathering.
This is the finished pattern: three pieces for the bodice, front ruffle with gathering, two pieces with gathering for the sleeve.