The attached pic shows the bottom of a container which has an inset of 5 mm. I have removed the supports which came off rather easily, but I'm not sure if there is more to be removed. The inset surface seems rather rough if it is actually the surface and not more infill. What do you think?
The support structure on the inside that you removed should have had a smooth flat surface. (like the raft) If you did not see this than I am thinking that is support that did not come out. I have found difficult to remove support from some large shallow insets like this. Get some dental picks and see if you can get under a corner.
It was indeed more support material I was able to remove with a dental pick and small flat chisel.
Linoleum cutters are extremely useful when support material is hard to reach/remove.
This one is really great too, especially for hard-to-get-at flat support at the bottom of a recess. Cheap hardware-store quality, but much stronger than dental picks.