Independent-Contracting Resources/Advice?

A Seattle tech-company and I would like to work together for a fixed-duration part-time data-science gig. As this isn't their mainline hiring strategy, they have asked me to explore independent contracting.

As I understand it, I have two options:

a) Spin up a company and handle all the tax/regulatory compliance myself, which looks a little daunting in Washington State.

or

b) Engage with a staffing agency, who may extract both a large ongoing cut throughout and expect a substantial finders-fee if I convert to full time.

I am interested in a) in the abstract, but want to keep my life simple these days. b) looks a little frustrating, given that both the company and I have already found one another, interviewed, and are simply looking for a way to make the legal connection.

Might anyone on HN be able to direct me to useful resources on the subject, recommend staffing agencies that are fair to all parties, or provide advice on which to choose?

Thanks!