How to handle custom text on a channel index page? I'm setting up a site with several channels, and the design requires an introductory paragraph at the top of each channel's index page (ie. before the list of entries) - essentially a post that corresponds to the channel's index page.

As I understand it, there's only a template but no entry corresponding to the index of a channel, so I'm wondering how best to handle this in Craft. I definitely don't want it hard-coded in the template, and ideally it should be somewhere reasonably intuitive for site admins to find and edit.

It feels like it should be straightforward to implement, but I just can't quite think how to do it. Any suggestions would be much appreciated!
I'd recommend to either give each channel's index page a dedicated single section or you configure a structure section to contain them all. An advantage of using a structure over separate singles is that you can generate the site's main navigation from it. And you can add a hierarchy to it.

The structure settings in the CP:

URL for Top-Level Entries:
{slug}

URL for Nested Entries:
{parent.uri}/{slug}

You probably want to give your index pages individual templates. To do this just add multiple entry types to your structure and relate each entry type with a template as described in the FAQs.