The one of the left is spalted beech, the other is walnut. No i dont know of any tutorial unfortunately. I just figured out how to do it myself, i have the right tools for the job though as i make knives so its easier for me than having to do it all by hand.
I made some templates from steel that i use to make the scales. If you dont want to make holes in the original scales then get a piece of softwood such as pine and after you have taken the original scales off, just press the metal body of the sak hard against the wood. The studs will leave imprints in the wood which you just drill out, then place the sak so that the studs are in the holes you drilled and mark around it. Cut it out and sand to the correct fit and you have a template you can use repeatedly. I did drill through the originals when i first made some, but i ended up making a better template from steel like i said. I've made dozens of sets now and can knock one out in a few minutes. I tend to use larger pieces of wood that have been through my thicknesser so they are already flat and of the correct thickness. I just drill them with a flat cut drill i ground myself, and cut them out on a small bandsaw.