Unfold a disjointed face or faces into the sketch plane.
On the ribbon 3D Model tabSketch panel, click Create 2D Sketch .
In the graphics area, click a face to set the sketch plane.
On the ribbon, Sketch tabDraw panel, click Project Flat Pattern.
In the graphics area, select a surface or surfaces to project into the sketch plane. Select faces that are connected to the sketch plane with bends, and that lie on the same side of the sheet metal as the sketch plane.
Create and constrain sketch geometry as necessary.