“Self-sponsorship” is widely used to describe a founder establishing or acquiring a UK business that obtains a sponsor licence and sponsors the founder as a Skilled Worker. It is not the name of an immigration route and it does not remove any requirement of the sponsor-licensing or Skilled Worker systems.
The structure can be lawful. Its credibility depends on substance: a genuine UK organisation, a properly governed sponsor, a real role required by the business, the correct occupation and salary position, and a worker who satisfies the immigration requirements. Incorporation, investment and a job title do not prove those matters by themselves.
The practical task is therefore not to package a founder as an employee. It is to test whether the business and proposed employment relationship can withstand the questions the Home Office is entitled to ask.