I applied online. The process took 6 months. I interviewed at NATO (The Hague) in Nov 2022
Interview
Hirevue virtual interview followed by a topical written assessment and formal interview with several staff including impartial panel members. Overall, not difficult, but competition is high so tends to attract strong candidates.
One way video interview with Hirevue. Did not talk to a live person. Fairly standard interview questions with a couple of minutes to record yourself providing an answer. Got rejection letter over email.