I applied online. The process took 1+ week. I interviewed at The Nature Conservancy in Apr 2017
Interview
They interviewed over Skype for Business, and it's two to three people interviewing you at once, alternating who is asking the questions. This interview was with the Colorado chapter and I'm not sure if other chapters conduct their interviews in the same way. I have interviewed for them twice now, accepting the first offer for a seasonal position, and not receiving an offer for the second, although the processes were very similar.
All that was required was a resume and a cover letter. I did both, reached out a few times, and didn't hear back as to if I was going to be hired or not.