With a mix of frustration at my decreasing work space from the spread of tools and envy at the success of colleagues with some of the 123D Make tools, I decided to throw together a quick pencil pot in my preferred CAD software, Alibre Design, and then slice and dice it with a preview version of Autodesk's 123D Make to make it ready to slot together after laser cutting.
Step 1: 3D Design
Alibre has a nice tree structure to the way you put together a 3D model. You can skip back and forth between stages of design and add new bits. Once I'd drawn the solid, I used the Shell tool to hollow out each of the uprights to the thickness of the material I'm using. In this case, 1/8" smokey acrylic. In this manner, I could easily go back and adjust it for a different thickness of acrylic, cardboard or wood.
Included in this step are the original Alibre file and the STL that was exported for use with 123D Plate.