By doing freelance work (like consulting, writing, designing… for example), you can learn how you solved it for that one person, what went right, what went wrong, and what they valued the most about the solution. Then do it again for someone else, and learn from it. Then again, then again.
Related: Do things that don’t scale.
Actually startups take off because the founders make them take off. There may be a handful that just grew by themselves, but usually it takes some sort of push to get them going. A good metaphor would be the cranks that car engines had before they got electric starters. Once the engine was going, it would keep going, but there was a separate and laborious process to get it going.
If products are all about scaling an experience, you need to figure out what that experience is. Then you start replacing the manual processes and handcrafted messages with smart automation and time-saving templates. Then the human effort moves elsewhere, like to enterprise sales or higher-tier support.