A method and a carrier medium carrying code to execute a method of designing a carton. The method includes accepting carton structural information, forming a 2D unfolded model of the substrate that when cut and folded forms the carton, and forming a 3D model of the carton. The method further includes displaying a 2D view of the unfolded carton design, and a perspective view of the 3D model. A user has the ability to manipulate the view of the 3D model, and also to select a flap of the carton on perspective view. As a result of the selecting, the method modifies the 2D unfolded view to be of the selected flap shown in an orientation suitable for designing the selected flap. The user designs the flap and the method accepts the design. The method includes modifying the perspective view of the 3D model to include any changes made in the design.