Get a piece of nicely figured wood,,your choice of type of course.
Lots of standard stuff like Walnut, (American & European), or go to the wilder looking 'Rain Forest' woods for some different colors.
If you are not making a Target Style grip and just a flat panel Service styl or Magna style, it's pretty easy to do with hand tools, patience and some skill.
A drill press is a great help and probably the one power tool among many that I would choose if only 1 were available and money was short.
A milling machine of course would be better yet as it can double as a drill press but also do the routing job and precise hold positioning/drilling.
These grips were made by sawing the blanks out of a piece of 1/2" thick English Walnut slab with a coping saw.
Since they are Service Style, they needed only be absolutely flat on the back and the upper portion inletted to meet the rounded frame cut and shoulders.
That takes time to do with hand chisels & files but a perfect fit is the result.
Clamp one panel in place and drill a blind hole to correct depth for the 'grip pin'.
Do the same for the other panel.
While the panels are still flat and not contoured,,mark and locate for the grip screw and drill it's location. Make sure it's correct or it may interfere with the mainspring.
Before unclamping &removing each panel, drill the countersink for that side escutcheon as well using the depth gauge stop on the drill press.
Doing it on the one set-up ensures the screwhole and the countersink are lined up/
(A piloted countersink cutter would avoid this but having one handy is not always how life happens.)
Sink the escutcheons into place in the panels. MAke sure you place the correct one on the side you want it to be. (Screw Head side on the correct side R or L)
Now mount the grips and use the grip screw to lock them down.
Then using hand files & rasps, shape them to near final shape,
Then take the last bit down with finer files and then grit paper backed up with a file or felt block.
Keep the bottom outline a smooth semi circle line. Draw one on the wood as a guide.
I often find an odd bottle, small can or other container that when placed on the edges of the frame where they meet the wood, presents the perfect arc line I want for the grips and simply draw a pencil line using the base of that container as the pattern. I think it was some sort of med bottle for this set. Seems to be plenty of those around lately to choose from.
Mark and drill, plunge cut with an end-mill cutter for medalions if using them.
Finish sand the wood. I usually go to 400grit and sand in the finish to 600grit.
Apply finish,, then checker if you like.
These I finished with a oil based varnish and checkered 28LPI in a pre-War Colt style pattern.
A set of orig 1920's 'forward facing' Colt grip medalions completed the grips. Medallions and escutcheons were gold plated.
It takes some work but it's a satisfying project.
Remember that plain fence post appearing wood will take just as long to complete a set of grips (or a gun stock) as a really nice piece of wood will.
It's your time spent.