Create map fro boardgame

[rich2005]

Try this:  https://youtu.be/oAJATFSESdU  duration 4 minutes

Nothing complicated, reall all about keeping parts separate. 
Making selection from map
Layer groups for land and sea Layer -> New Layer Group
New layers for sea / land and sea-edge / land-edge Layer -> New Layer
Stroking the selection  Edit -> Stroke selection
..and various selection inverts and tidy-ups.