(I've been in my new job for 4 hours yet I'm still worrying about Flow content models. Such loyalty :) )
Good news: if you have the flow-create-board right, and if you're on a wiki with $wgContentHandlerUseDB set, then add-topic or edit-header creates a new Flow board. \o/ T76793 is resolved.
However, neither condition is set on enwiki. I added some more blocking tasks to T78640 https://phabricator.wikimedia.org/T78640 (Co-op: bot can create a Flow board for each new mentored editor (tracking)).
Frances, do you have a wiki page explaining what the bot will do? Are you or ErikB (who comes back from break on Friday) working on T76785 https://phabricator.wikimedia.org/T76785 (Co-op: get approval for hostbot to flow-create-board right) ?
I explained the issues to Danny that make T51193 https://phabricator.wikimedia.org/T51193 (Set $wgContentHandlerUseDB = true on all WMF wikis) contentious. I moved its blockers to a new T85847 https://phabricator.wikimedia.org/T85847 (issues with granting the editcontentmodel right). We'd rather the Co-op bot *not* be tied to big discussions of changing content models and Flow taking over more talk pages, but it might get sucked in.
http://etherpad.wikimedia.org/p/editcontentmodel has next steps for wgContentHandlerUseDB and a draft message about the changes for a Flow tech lead to eventually send out.
I'm happy to help, but someone else needs to take the reigns rains reins on this.
-- =S Page Collaboration team engineer