Yes, you can, use less liquid as it doesn't reduce, I use about half what I'd normally use. Very nice is a chunky crab gumbo, tin of toms, onions, garlic, about 300ml stock, pureed cannelini beans (these thicken the soup) s & p and a tsp hot chilli powder. Cook for about 5 hours then add a tin of dressed crab, some shredded greens or cabbage, leave for another half hour, and serve with crusty bread, and maybe white crab mixed in last minute.
I really dont like stews or soups made in a slow cooker, they just turn out vile I think I use mine for making cheap cuts of meat tender and tasty. I stick in ribs, or pork shoulder, or brisket etc and they come out fantastic.