Founder of Zencastr here. Hopefully this is helpful to other solo founders. Happy to answer any questions here if they arise :)

Joshontheweb I love zencastr. A lot of the guests have mentioned that the UI is really good. What was the process of designing it?

Thank you!

Hmmm.. As far as the process for design. I use Sketch 3 to prototype the design. I definitely stretched my abilities a bit as I'm not usually a designer. I basically just tried to focus on ease of use and to make it feel nice to use. There is certainly more work to be done in this area.