Well, I'm making one right now for my Busse BATAC. It's my first and I couldn't find (mostly didn't try) any info on working cordura, so I'm making it up as I go along...
Take a look at how manufacturers put the stuff together, on knife sheaths and in my case old laptop bags (great source of material). The seams are usually folded under to hide the cut edge, and edges are often stitched onto a ribbon/tape.
A tip on cutting up cordura; use a heated craft knife. It seals the edge as it cuts.
I'm using a combination of epoxy resin designed for plastics, Evo-stick serious glue (yes it's really called that) and old-fashioned stitching to fasten the cordura.
The insert is made from some thin, semi-rigid plastic mouse mats. I'm using the shoulder strap webbing from the laptop bag to make the belt loop.