The process was very informal. I was not sure I was participating in an interview at the time. Mainly consisted of a series of conversations with different personnel. Because of the structure, you interview with the CRFP head as well as with ARI personnel.
I applied online. I interviewed at US Army Research Institute
Interview
At the time I was hired, I had to do a job talk (present on a research project). I presented on work I had done in graduate school; the range of folks attending my talk included included GS12s to GS15s. Overall folks were welcoming but also wanted to gauge my ability to present research/scientific info and my ability to defend my work.
Interview questions [1]
Question 1
Mostly questions about the research I presented as part of my job talk to see how I responded to off the cuff questions; questions on why I wanted to join ARI