I didn't know what I was really doing. I had bought a set of replacement scales on eBay that were made out of wood, and when I put them on I managed to crack one of them, and they were way too big and long for my blade. That's what prompted me to try making my own. I looked at a few of my other razors and tried to eyeball the distances and ratios that were there, watched a couple YouTube videos, then just "winged it".

I'm happy with how they turned out, and they are comfortable while shaving and stropping, which was the important part for me.

I have another razor with crappy scales, so I may try it again.