instantiate gameobjects into area

How can I achieve this?

I have a list of vector3 that are benchmarks.
I would like to instantiate an object within the area between points, as the image shows.
the idea is to do it without using colliders146473-ref.png

As mentioned in the source link below. You can triangulate the polygon you are specifying with the reference points then you can use triangle point picking to add the point to those triangles.