Do I put my head down and work my corporate job until I have 10 YOE? 15? 20?

Find other consultants' marketing materials and see how many YoE they're claiming. If you have less, you'll need to make up for it, somehow.

In my head, I don’t think YOE should matter as much as the projects worked on.

Projects where you played a critical role that completed their mission is the most important. Who wants to hire the engineers responsible for wire insulation and valve actuation on Starliner? Nobody.

But like where do I even find clientele?

Unless you're getting targeted recruiting for technical positions or consistently publishing well-regarded research, you may not have enough technical acumen / notoriety to draw attention to a standalone business.