How do I start a new peer-reviewed open access journal? I'm an academic and would like to start a scholarly journal. My reasons are manyfold: primarily I want an open access journal, and think that my field needs an own journal.

How do I start a new open access journal?
You shouldn't do this alone if you want to have a respectable open access (OA) journal in your field. The first time after launching a journal is critical: You need a good editorial board and a sustained amount of good submissions until you achieve a good impact factor. This is pretty much impossible without the help of an organization or a professional publisher.

You are probably a member of some kind of scientific society which is active in your field. I suggest that you get some other members on board with this idea and lobby for the society starting an OA journal. There are quite a few OA journals that have been started like this. An example from my field are the EGU's open access journals, which are a huge success.