How to start a platform based product without having an initial audience

Hello everyone, I listen to many different founders and their stories on how they get started with their ideas and validated them through their existing audience. I have seen a common trait in all of them, they have an initial audience that believes in them and is their first customer. I have ideas that I want to work on which are more platform based like product hunt, and indie hackers, but I fear how can I get my first few users and validate the idea. I know making up an audience is also a part of the business, but right now I can't think I can leave everything and start creating an audience just because I want to launch something and want them to be my user. I believe creating an audience is a natural process and needs time. What advice would you give me in this position in order to get some validation on the idea and get some initial traction? Thank you