I'm kind of a jack-of-all-trades, so I did all of my own design. I don't know that I could get hired by a big company to do design work, but I'm good enough to make my own UIs.

One thing that has helped a lot is doing a lot of "hallway" tests: you watch someone sign up, then you cringe at how bad your UI is, then you fix it.

(I'm the guy behind https://indiehackers.com/businesses/complice)