I just leave the string on, so it all keeps together. In the bottom, I add just under a cup of liquid. I did a slow cooked roast beef today and I mixed up about a tablespoon of molasses (you could use brown sugar), some worcestershire sauce, a bit of tamari sauce, a dab of apple cider vinegar, 3 or 4 cloves of garlic, some dried herbs and some water. You could substitute red wine for the water. Mix it up and add to the slow cooker. Then sear the meat in a pan on all sides before adding to the slow cooker. I use a wok as I find it sears things better. You dont have to sear the meat, but it does give it a better flavour. I had the meat with fat side on top, so it flowed down through the meat as it cooked.

For lamb, I recently slow cooked 1.5kg with a similar gravy mix as above for about 6-8 hours on low. For the beef today, it was about 4 hours on high.

Once cooked, take it out and let it rest, covered, for 10-20minutes before carving. As it rests, I add some cornflour to the juices to make gravy.