Nieman Storyboard is an "online resource" on the art and craft of nonfiction storytelling. They're published by The Nieman Foundation for Journalism at Harvard University. They accept pitches from professionals and students. They publish articles on the craft of nonfiction. They want "stories that go behind the reporting, writing, editing, production and ethics of story work produced across platforms — or about the people producing that work." According to their guidelines, rates start at $200, and can vary depending on time and level of effort required. To learn more, refer to this page.