Is there a simple “how-to” somewhere on how to make an administrative boundary change and submit it?
How to get help making a boundary change to an administrative boundary
The information is kind of scattered on the wiki. Here are some articles that cover it:
To summarize all of that really quickly, you’ll have a relation with all of the boundary ways as members (role=outer usually), and a node as member (role=label). You may also have a node for the capital or city hall (role=admin_centre)
The relation contains tags describing the administrative area, like name and wikidata. It must also have type=boundary, boundary=administrative, and admin_level=*. Get the admin level for your country from the table on the boundary=administrative page.
The label node also has the tags describing the area. It also has place=* and admin_level=*.
The boundary ways don’t have to have tags at all, they’ll just be members of the relation. But you can optionally add boundary=administrative and admin_level=*. Also if the boundary is a river, it will have the river tags.
Working with relations can be a bit complicated. If you’re using JOSM I’d be happy to give you more pointers. I’m not sure how to do it in iD though.