I've been asked how I go about making these holsters so I did a very short tutorial on the steps I take to make one of these holsters (the IWB for the Tokarev specifically).
1. Create a paper template which is used to judge how much kydex to use and the general shape. I used the gun for this part and taped a chopstick to the top of the slide for the sight channel.
2. Using the template I cut the kydex using metal snips.
3. Usually I'll put the whole piece of kydex in a toaster oven set at about 225 for handful of seconds watching it till it starts to flop and then take it out and wrap it around the gun and add pressure. In this case the kydex was a little too long to fit in my small oven so I took a different tactic. Using a heat gun I did an initial fold on a soft & squishy folded blanket. Wear gloves from here on out to protect your hands. Things get hot.
4. Then I focused on different areas heating and pressing to make it a snug fit. I indent the trigger guard a little extra for retention, pulling the gun out before it gets completely rigid so that it's not too tight.
5. Once the fit is right I used a leather punch to make the holes for the rivets. This works for the thin kydex for thicker stuff you'll need to drill the holes. Then I punched the rivets in and tested the gun fit again.
6. At this point I start trimming off overhang with the metal snips.
7. The clips are integral with the holster so they are formed after the mold of the gun has been set. I cut out the general shape for the clips as if they were straightened out and using a 1.5" wide paint stirrer cut in half as my "belt" & "pants" I heated the clips and started folding them around the stirrers. Then I cut off the excess length.
8. Test the fit one last time and if it's too loose use folded wet paper towels to protect the molded sections that don't need adjustment and then heat up the parts that do and add pressure.
9. Once everything is cut & fitted then comes the time consuming part, finishing. My preferred tool for finishing is an emory board. Keep several of different sizes on hand for some of the hard to reach parts. Sand all edges and corners so things are smooth to the touch. Do this part well and it'll look professional, do it poorly and it'll look like Bubba made it with a dull knife.
This is a very general writeup, but it'll work for most single sheet kydex holster designs.