There is a group of them around the base of the forst (obviously)

There is a group of them on top of the hill behind the fort

There is another group of them on top of the hill a little ways north of the previous group

There is yet another group of them on top of the hill a little ways north of that group as well. (translated: there are three groups kind of in a line behind the fort going north that stretch near to the edge of the map IIRC)

The fifth group is going to be just north of the inn you pass if you are following the road from Ravenshore... there are a few garbage piles and one cauldron there as well.

If you are inside the fort, you walk around, and your characters status button goes from green to yellow... that means you haven't cleared the dungeon entirely... check every nook and cranny and use your map to help find em.