"place them where you want", they said. But if you want a consistent world, not every placement will make equal sense. Find thoughts and inspiration on where (and why) to put the Raven's purge sites.
Beware:
Spoilers ahead
Although your GM might have an entirely different view on the world. You have been warned, though.
Grindbone
Slavery is, understandably, a red flag for many and I have some issues wether it would be lucrative at all. Grindbone is purposefully located at a river; bear in mind that bloodlings can't manifest over water. A hex in the center will work well, on W26 most of the map will be reachable by waterway