A method of forming a workpiece having an initial heat treatment and made of a naturally aging alloy to a final shape using an incremental sheet forming (ISF) machine having a coordinate system and a tool path corresponding to the final shape of the workpiece is disclosed. The method comprises positioning the workpiece in the ISF machine; performing an initial forming operation on the workpiece using the ISF machine; performing a final heat treatment on the workpiece; repositioning the workpiece in the ISF machine; and, with the workpiece in a final workpiece orientation in the ISF machine and the tool path of the ISF machine in a final tool-path orientation in the ISF machine, performing a final forming operation on the workpiece using the ISF machine to achieve the final shape of the workpiece. Intermediate heat treatments and intermediate forming operations in the ISF machine may also be performed.