I make them! It takes lots of time & perfecting to get it just right, & some of the patterns still aren't quite what I want them to be. But I'm going to school for that, so it's okay. :) The only thing that isn't 100% originally mine is the back curve--I drafted that from a well-fitted jacket I own because I couldn't quite pinch & pin in the back.

But an abbreviated description of my process is this: I start out with an oversized pattern that I either draw out flat or drape on my dressform--something that fits in the neck & has the right armhole length, etc.--& then I put it on and basically pinch & pin the bust/waist/hip curves til it's mostly even on both sides. Then I mark in chalk, un-pin, trim down the excess fabric, & try to make things symmetrical. I usually make a mockup to test the pattern, tweak whatever needs to be tweaked, & then it's set to go.

Sometimes I try different things... for my patchwork dress, I covered a bra cup in tape & cut it apart! I had to teach myself everything I know, so I probably don't do things the right way. But it works okay for me!

One more thing (in this massive, wordy answer)--you will be able to find basic dress patterns in all the pattern catalogs in your local fabric store. Just look at the flats instead of the sketches & photos, & they'll probably have a few of each style that are just basic that you can work off of. You have the wonderful power of being able to cut things off at the waist & just use the top, or of mixing two patterns, though I've never tried that so I can't tell you how easy it is! But have fun, no matter what. :)