A 6″X6″ square is more than enough Kydex for a holster, but you may want to upgrade to the 12″X6″ if you are working with a laser or light. The 12″x6″ size can be cut in half for two pieces if you are afraid you may mess up the first piece.
Heat the Kydex at 325 degrees for about two minutes. Make sure the gun is pointing to the left for a right-handed holster. Place the Kydex on top of the plywood with the shiny side up. Place the pistol on top of the Kydex and center it in the cut out. Close the press and tighten it down. Let it set for at least five minutes.
The Kydex should be formed exactly to the shape of the pistol. If not, reheat and repeat.
Line everything up how you want it and draw circles where you want the holes to be. A regular pencil works just fine.
After the holes are drilled, place the Kydex back on the leather and use a pencil or a punch to mark the holes on the leather.
After the holes are drilled in the Kydex and the matching holes are punched out of the leather, assemble the Kydex body to the leather. Sketch out the design you want with a pencil.
You can use tin snips to trim the Kydex. (A band saw works much better).
Finish the edges with sandpaper. A Dremel will make quick work of this, but it is not necessary.
Assemble the body to the leather with the spacers in place.