What are the steps to find a publisher and strike a deal to publish the proceedings of a workshop? I help organize a workshop in a conference on machine learning where the conference doesn't publish proceedings for the workshops: the workshops have to do it themselves if they want to.
What are the steps to find a publisher and strike a deal to publish the proceedings of a workshop? (where to find the list of publisher in a given field, what are the typical contract clauses and negotiation points, etc.)
I know that we can publish it ourselves (since in the end publish = hosting some PDFs online) but I'm curious to know how the old-fashioned publishers work.
If that matters for the answer, all papers are written in English and one requirement is that papers are open access or allowed to be posted on arXiv.
I went through this a few years ago for a conference for which I was the program chair.
Since you want open access, you'll find that the big commercial publishers will want to charge quite a bit (thousands of dollars per paper) to publish your conference proceedings.  For open access publishing, there are a few reputable publishers and lots of disreputable publishers that you'll want to avoid.
One reputable publisher for topics likes yours is Dagstuhl's LIPICS series.
If the society that sponsors the conference has its own in-house publishing arm then that can be a good choice too.