The interview process was fine. The Co-founder reached out to me on LinkedIn and I didn't do anything about it until my coworker suggested I meet with them. So I did.
My biggest red flags were: I did not have a formal job title or job description for the "role" I was interviewing for. Nor did I have a salary range. They asked me several times for my compensation expectations, I replied that I would be flexible for the right opportunity. And in return I received ZERO clarity. Very frustrating.
Regarding the interviews, I had two phone interviews: one with the Co-Founder and the other with the Founder and CEO. Both were informal but covered a lot of basics. The third interview was in-person. As others mentioned, I had to create a slide deck and present it. I sold them on the slide deck and then they chatted about my current product. I told them I would pitch them my current product, I did and at the end they looked at each other and said, "we should consider their product in the future!" In my mind, it could not have gone any better, I got positive feedback on my deck as well as created interest in something else. Clearly I was wrong.
I was ghosted.