I want to start from scratch. Is there a list or map showing the avaliable places to build? Thanks. (I have the guide but can't seem to find anything about this)

Well, Sanctuary Hills is one, as is the garage not far away.

So far I've found...three other locations that can be made into...Workbench Settlements as the game calls them. Small places so far to build up from humble beginnings. Haven't found any blank slates yet.