You could design them in 3D something like Solidworks/google sketchup, but unless you especially need it in 3D I would stick with just drawing each panel in 2D. That way you can convert the 2D to gcode easily with something like CamBam free edition, which is what I use. 3D cad programs generally have facility to turn a 3D model into 2D drawings, but I think you will find that doesn't lend itself easily to importing into CAM software.