Well first off, the wood would have to be dried throughly. Otherwise it can warp and split.
Regarding the whittling of a set of scales, sand the insides of the scales flat on sandpaper on a tile.
Then mark the stock tang on the wood with a pencil and you will be leaving the rest of the material for support within the handle.
Carve around your marks to make the internal part stick beyond the scales then later sand that to flush with the stock handle.
Create the other side keeping the inside flush to the stock handle, no internal posts or valleys.
Doing this would leave you just to drill and countersink your holes, mount the scales and then all you would have left to do would be shape the rough with sand paper.
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Good luck and keep us posted!