Just tell them the truth. I'd been laid off on Sep 7, 2001, and sent out green card application in this Feb (my H1 was expired in May 2004,the application is family based as well.). I got interviewed on this passed Monday. They didn't stamp on my passport, but this is not because the period of black status gap, it is the FBI background check holding me on the process. This is really thing you should worry about.