Board Thread:Questions and Answers/@comment-1620907-20151127200839/@comment-24909831-20170812061858

Yes, Foundings don't happen in an instant anyway... I guess it is just fine then.

But actually Mars, or Cawl, and Guilliman did indeed just have all the gear for Primaris marines lying about. And building a fortress monastery doesn't really take much time, at least if we look at the Dark Imperium novel where it is done in time of weeks.