That last link is the American Bar Association explaining how to do it.
(Experience in law firms may actually work against you there. In big companies I've worked for, none of the people working there had any idea how to start their own business, and would try to convince others it was impossible.)
http://info.legalzoom.com/can-lawyer-sole-proprietorship-248...
https://www.americanbar.org/groups/gpsolo/resources/solosez/...
That last link is the American Bar Association explaining how to do it.
(Experience in law firms may actually work against you there. In big companies I've worked for, none of the people working there had any idea how to start their own business, and would try to convince others it was impossible.)