Well, let's see, maybe I can get you started on the right track. To get started, you could make yourself a plexiglass template. You can see one in the picture. There is a grip pin hole in the plastic template, you just can't see it. You can also see how I used a thin piece of wood to locate the lock cut out in my grips. Once I got the lock hole just right in that template, I use it to make a router jig to route the recesses in the backs of the grips.
But anyway, back to the plastic template. Get yourself a piece of 1/8" plexiglass and cut out a rectangle large enough for a wood grip. Place this piece over your grip frame and mark where the grip pin hole should be.
Drill the hole in the plexiglass. I used a #21 drill which is .159”. It’s large enough for the grip pin to fit into nicely.
Once you have that done, you can lay your template on the gun with the grip pin in the hole. Now take a ball point pen and mark where the vertical and horizontal parts of the frame make up the top corner of the grip. Of course you can see this through the plexiglass.
Now what you have to do is very carefully trim that top corner of the template so it just fits into that top corner on the grip frame. This is where a small disc sander comes in handy.
Once you get that done, you are ready for the wood. It should be cut into two blanks now. Make sure the backs are completely flat. Place your template on the wood where you want your grip and mark where the grip pin hole is in the template. Now drill that hole in the wood using that #21 drill bit. You only want to drill about .180” deep.
Once you get both pieces of your wood drilled. Lay the template back on the wood and stick the drill through the template into the wood like a pin. Now mark that top corner of your template on the wood.
Once you get that done, you need to trim the top corner of the wood to fit into the grip frame just like you did the template. Depending on what kind of grips you are making you may have to put the little angle cut into the back of the grip to clear the angle on the grip frame. You can do this with a file.
Once your wood sits fully on the frame with the grip pin in the hole, you can mark the outside perimeter of the grip right from the frame with a pencil. Now that you have that outline you can carefully cut out the grip shape with a small band saw or jig saw leaving just enough excess to hand fit to the grip frame.
I know you are making only one pair of grips, but I would strongly recommend that you purchase an oscillating spindle sander for shaping the grips. You can get one for around $200 or less and it will save you a whole lot of hand work. Your grips might even turn out so nice that you want to make a couple more pairs making the purchase of the sander one of your better moves. This should at least get you started. It’s how I made my first pair of grips. Lots of people try making a pair of grips with nothing but a file, a hammer and a pair of pliers. So without the proper tools they try to hurry and get the grip made. They just wind up screwing up the wood and throwing it away.
Sure, one can whittle out a pair of grips with a pocket knife if they spend enough time doing it. But as I said most people start with inadequate tools and try to hurry to much and just wind up screwing things up. Take your time. That's the best advice i can give you.
One more thing. Make sure the wood you use is dry. Should be between 6 and 10 percent. No point in making yourself a nice pair of grips only to have them start shrinking and cracking on you.