I do holster work, so I'll try to help you out. Honestly, might be cheaper to buy one but here goes.
You'll need:
1) a cutting tool. A single edged razor blade will work. X-acto knife is better. I have a patch knife that I use.
Looking at it a second time, you'll have very little cutting to do=just a little trimming at the end.
2) a metal edged ruler for aligning cuts. All steel ruler works the best.
3) Something to burnish the edges. A smooth piece of hardwood will work. A piece of hardwood dowel in a drill press should do pretty well.
4) Something to cut round holes.
5) A leather finish and a softener. Maybe a dye.
Steps:
A) Cut belt to width you want using the straight edge and the razor blade. Measure twice, cut once. I recommend clamping everything down, so things don't slip.
B) Measure and punch holes at ends in order to fold ends over slung loops (metal parts). You can secure them with pop-rivets, chicago screws (screw fasteners), screw back conchos (look good) or leather bootlaces (stronger than leather lace)
C) Burnish edges to smooth out. This is done by polishing with the wooden dowel almost to the point of scorching the leather edge. It helps to polish with the finest sandpaper you can find==that might be good enough.
D) Finish leather. You might want to dye it. If you have access to walnut hulls or coffee, you can brew a SUPER-STRONG solution (boil for hours!). This makes a nice dark brown. For black, use vinegaroon. This is made by soaking iron in vinegar. Set a pad of steel wool on fire. After it burns out (the impurities are gone) put it in a jar of plain old vinegar for a couple of days or so. Brush it on the leather (test it on a scrap first). Might need to do it a couple of time. This makes a very good TRUE black (not a dark blue). Leather will be very stiff. Apply several coats of softener--I use Olive oil. Neatsfoot will work. Or buy some expensive cream. Put in a warm place (such as out in the sun) Preserve and weatherize with saddle soap
or Skidmore's dressing. Some paste shoe polish if you want.
My cost for this priceless (price=worth, right?) knowledge? Post some pics when done?
PM me if you have questions.