To make the shaped on the front, start by tracing your front blouse or bodice block and mark a point 1" from the neck edge, along the shoulder line.

From there, draw a line 4" down, perpendicular to the shoulder line (keep the intersecting line at 90 degrees, squared).

On the center front line, mark a point 3" down from the neck edge. Draw a curved line from that point to the end of the 4" line.  This new line should have a gentle curve up, towards the face.

The back is even easier to do! Just "scoop out" 1" along the back neck.

Mark a point 1" from the neck edge, along the shoulder line and another along the center back line. Simply follow the curve of the original neckline, but 1" away.

The width of the back neck and shoulders will now match the front, with just a bit of openness at the back.

The shape can be adjusted as you prefer - wider, lower, a more extreme curve, or higher and more gentle and modest.  It all depends on your taste, and the particular dress or top you're making.

This is a great look for a grown-up party dress, and makes a very nice "dress up" look (in a bit more modest draft) for a little girl's dress, too.