Showing outer faces to create borders with face culling or mask?

Heyy, me and my friends are doing a sea exploration game with a hexagonal tile system, we wanted to do highlight areas using borders like the image below, what’s the best way to do something like this (preferably using only the shader graph without code)?

We thought about putting the meshes like this but then we’d need a method to show only the outer borders and hide the inside like the previous image

We’re trying to instantiate meshes cause it gives more liberty to do something like this but we don’t know whats the best way to do it, what you think?

You could just make one edge and put as many as necessary around it…

we could but like, wouldn’t that make it more difficult? Since we’d have to code in which position the edge is on the grid, the rotation of the edge or edges, how many edges are in one single tile, etc? Since its procedural and every tile works on a grid system, or you meant another way of doing it?