The case was modelled by John Forth using PTC Creo and is described in the PDF guide contained in the ZIP file. The case was modelled from DXF files John downloaded from the web. Once you have the case as a Creo model, it's very easy to modify or adapt the design. John's description is below.
Many of you will be getting to grips with the Raspberry Pi computer that arrives bare bones, i.e. no case. On-line there are many examples of cases you can purchase but this one comes courtesy of just a DXF file for use with your laser cutter. Reverse engineering it to make modifications and to personalise it you can use the DXF file to create features and parts in CREO. This short tutorial tells you how to do this. You can then produce your own DXF file from your CREO model and use it to cut out the parts on a laser cutter using acrylic, foam board, plywood etc. I hope you enjoy.