title_body: Is it possible to airlock a V60 brew?
upvoted_answer: Looking at the question from another angle, there’s nothing that would prevent an airlock, except your little pieces, of course.
  The chance that the filter holder and the cup rim fit so perfectly for an instant lock is slim, but you shouldn’t underestimate the power to a bit of condensation when it comes to creating a seal. I had a similar problem just the other week when bottling hot syrup with a funnel without ridges: The first one or two were fine, after that, I got that splashing whenever the water film tore for a moment and ultimately had to lift the funnel ever so slightly over the bottle rim to ensure a steady flow. I have had issues with airlock when using a porcelain Melitta filter holder, so I can totally confirm that some types of filter holders do tend to seal.
  Even one of your plastic pieces should already be enough to prevent the issue.