The easiest way? Angelist.

I’ve poked around – looks like it’s not enough to just declare you’re an accredited investor, but also prove it?

What evidence do I need to provide as a US investor: https://help.angellist.com/hc/en-us/articles/15569926884109-...

As a non-US investor: https://help.angellist.com/hc/en-us/articles/15570114297869-...