This is how I make the pouch type sheath for the BATAC, this one is going to be Dr. Lundes, I am sure he could have taken better pictures.
First thing is tools you will need. From left to right, a skiver, a # 2 edger, knife, compass, pen, ruler.
Make a template out of thin cardboard, I set the knife down and trace the outside contour with the compass making the template about 1/2 inch larger than the knife. I then tweak the template so it looks nice. Trace the knife onto the template.
Lay the teamplate on top of your leather and cut the pieces out, one of them is reversed for the back side. The front is missing from this pic as I had already wet it at this point and I forgot about it. This picture also shows the belt loop which I will sew on the back later.
Set the knife on the backer piece (not the back piece) this will make sense as we go along. This should be skin side up.
Press the handle into the leather so you can see the outline of the handle. Mark it and cut it out also leaving room for the handle to slide in and out.