Schmedlap:

I would suggest that you stress some of the following issues:
1. experience in foreign countries
2. interaction with foreigners and understanding of foreign cultures
3. understanding of, and experience with, the interagency process
4. leadership experience
5. program management experience

At the risk of impugning your intelligence, I would also advise avoiding the following:
1. personal political, social, or religious opinions
2. personal views about foreign policy execution
3. pronouncements about grand strategy

A caveat: I do not know any FSOs who have actually served on the Board of Examiners (the entity that conducts the oral interviews). These positions are open to FSOs of any cone who have the appropriate rank but this is a niche area outside of the mainstream - not an assignment that usually attracts the ambitious or those identified as water walkers.