Potato flakes are so cheap I usually don't bother doing it myself. But the way I do it (the lazy way

), is to run them thru a juicer.
That takes much of the fluid (which is a natural thickener and can be used to make other things, like gravy... mmmm! ) out already, and purees the potato, skin & all! I dehydrate that & then use a food processor to pulverize it to flakes/powder. It's so fine that when I pour boiling water in to reconstitute it, the absorbed water cooks it as well.
P.S. the generic magik-bullet is the gadget I use for the above, it's compact and uses little electricity.