[Crex]

Good advice up there Kev. Most of the really used tools are so simple that once you have one and work with it, you will wonder why you didn't just make it yourself.
Belly leather is better suited for things other than sheaths and holsters where rigidity or stiffness is important. As Ray stated "Not Belly".
If you like the integral belt loop, simply learn to fold it over into the inside. Skive the tag end so it will lay flush, glue it down. Cut it so it will be secured in the welt stitching as well as a simple line of stitches across. Make sure you finish off the cut edges of the loop before gluing and stitching down. Be careful with the glue as it is stain resistant and will show in the end.
I also finish off/burnish my edges with worn out belts on my grinder. Usually start with a slap worn out 220 and then a 400. Little trick is to wet the edge just before doing this with a damp sponge. Helps greatly with the slickin' up process. Also make sure you use a dust collector and mask as organics like leather are just as bad for your lungs as any other dust and often carry mold spore (yeah most leather is exposed to and carries mold spore of some kind). Be safe.

ps - as you have noticed by now fresh wet leather will pick up and hold any and every speck of dirt in your shop and on your hands. Got to keep things clean.