Isometric Map Editor in Unity

Hi!

I want to do a Isometric RPG Game and i would like to make easier the process of making the maps, so how could i do something like this inside Unity?

I don't want to use a extension that do all the work for me, so that's why i here to ask if some of you could have tips of how to start a isometric map editor from scratch or show me a tutorial about it that i didn't found yet.

Thanks in advance!!

Here i will put some stuff that i've already watched/read:

Paul Metcalf Tutorial -

tbswithunity3d Hexagon (not what i'm aiming to do) Tactics- https://tbswithunity3d.wordpress.com/