I-140 experience letters for self-employed independent contractor

[alexcee]

Hello, I need to confirm that I have 1 year of qualifying experience that is part of the job position requirements for EB type of Green card.

• I came to the US on H1B to work for the US Company 1.
• After less than a year with the US Company 1 I've transferred the H1B to the US Company 2 to start the EB petition.

Now the US Company 2 has initiated the PERM and I need to provide EVLs to confirm that I have qualifying experience.

• I've got one EVL from the US Company 1 for less than a year that states "full-time and 40 hours/week". That's okay.
• Now I need another EVL for the rest of one year.

Prior to coming to the US, I worked in my home country as a self-employed consultant, and I had a service agreement for provision of services for the US Company 3. So when I worked from abroad I've got directly paid by the third company the US Company 3.
Since the agreement between me and the US Company 3 was an agreement for the provision of services and not for the employment - what is the best way to confirm the hours of work for the purpose of a confirmation of getting qualifying experience?

Thank you!