+1
1-piece scales are easy to make with the right tools. I personally use a tablesaw with a jig to cut the slot, then a hand saw to finish. I then have some stock already cut to exactly match the kerf of my tablesaw blade so that I can wedge it in there to continue cutting out and shaping the blank.
You might be able to cut the slot with a hand saw, but your slot may not end up as straight. There is nothing, to my knowlege, that can be done with power tools that can't be done by hand in some way. However, they make the job much faster, simple, precise and in some cases safer.