I applied online. The process took 6 months. I interviewed at Defense Language Institute Foreign Language Center
Interview
Before the interview, you have to take OPI exam in English and your native language. If you pass it, there will be an interview, which lasts up to 60 min. The interview is not easy. The questions are about teaching experience and there are scenarios with some issues you have to solve (normally student-teacher scenario).
Interview questions [1]
Question 1
How can you increase a student's proficiency level?