Love my slow cooker too, mostly casseroles.
Have tried it for currys in the past, it did not seem to work well.
But always use the leftover roast meat from the weekend for our curries, so do prefer making a curry in a pan, with a pre made sauce taht have done in a slow cooker.
Think its the best way for a slow cooker is to make a curry sauce in it, freeze and reheat the sauce with meat and veg later.
Have though recently made a great chilli a few times with minced beef, onions, garlic, plum toms, my frozen tom puree.
All fried till minced and onion browned and then added to slow cooker with cumin, chill powder, worcester sauce and fresh herbs for 4-5 hours.
About an hour to go, add beans and mushrooms. I've used my garden frozen borlotti beans and broad beans, instead of the kidney beans that noone really likes.
It was a great incentive for me to grow more of those bollotti beans that were a great success growing last year.