I am an enduring Greyhawk fan. I’ve been running campaigns in my beloved Greyhawk since the mid-eighties. When I started Raging Swan Press, one of my design goals was that anything we published should be easily portable into Greyhawk.
That’s one of the main reasons why I haven’t designed my own comprehensive setting. I get a steady stream of questions about how the Lonely Coast and Ashlar fit together and requests for a world map. That’s not really what I’m about. I much prefer designing things a GM can plonk down (that’s a technical design term) in their own world pretty much wherever they fancy or need it to be.
For example, the Shadowed Keep on the Borderland essentially requires a small town and a relatively isolated piece of woodland—preferably on a borderland. Such locales are easy to find in almost any campaign.
Similarly, both The Lonely Coast and Duchy of Ashlar are small, independent realms. Each would only fill only a hex or two on the Greyhawk map—and there is a lot of empty space in Greyhawk.
So, if you ask me where things “should” go in Greyhawk my answer is: wherever works for you!
If you pushed me, though, either mini-campaign would work well in the vicinity or Ratik, southern Keoland or as a replacement for Dullstrand.