Since we all understand that you are not into this for economy (the energy cost per gallon for a simple still is pretty high, and reverse osmosis wastes a lot of water) I can in good conscience tell how the one we built back in the '60s worked. (This was North Alabama on TVA electricity, really cheap at least back then, and we had our own well so the condenser water was not a big issue.)
A large stock pot sat on an electric hotplate; through the lid of the stockpot a 1/4 copper tube fed water in through a float-operated valve built out of carburetor parts. The "worm" was closely wound copper tubing inside the one-inch brass standpipe from a toilet. Well water went in and out of the brass pipe from bottom to top, so that the warmest water left where the steam was coming in. I don't recall what we used to seal the worm (condenser tube) to the brass pipe, but it was probably either brass washers or discs made out of flattened copper tubing, all soldered together.
This was it, basically. If memory serves, production was about a gallon per hour of not exceptionally good water. It turns out that unless a still is pretty well designed, a fair amount of water gets carried out in the form of droplets; for Mom's steam iron or making up developer, it was fine, but I wouldn't put this rig up against anything made by Barnstead or Corning.
A few details have been lost from memory, such as how we sealed the penetrations for water feed and steam removal to the lid of the pot. But if I were going to do it over again, a few minutes in the MSC, McMaster-Carr, or Grainger catalogs would locate things like bulkhead fittings and float valves. If your water is really hard, and you want a lot of water, first buy stock in your local energy supplier and then rig an overflow so that there is a constant wastage of water from the boiler, to carry off the concentrated salts. Even then, you will probably have to de-grunge the boiler fairly often, since the ever-present calcium and magnesium will make a scale that insulates the bottom and spoils heat transfer from the hotplate.
There. Now aren't you glad that you asked?