Okay here is the low-down on the Escaped Slaves.
1) They only spawn on the second island.
2) Time of day means nothing!
3) Go to +2600 +1900 There is a single standing column - use that as your place marker.
4) Kill everything you see in all directions.
5) Check every froglock - after you clear the island escaped slaves appear BEFORE the escorts and AFTER the escorts.
I looted 6 shackles in 2-3 hours!
I had hunted in the newbie area 4 hours prior and never saw an escort or an escaped!