2D NavMesh in runtime - Is there any tutorial?

Heho!
(Beginner here)

is there any tutorial on how to make a custom 2D Navmesh which can be baked at runtime?
I found this in the asset store:
https://forum.unity3d.com/threads/n...igation-for-your-2d-projects-released.231022/

But I am poor and cheap and also I would like to learn it.
(Edit: I also just saw that it's down anyway)

All the best!