Yes! The sauce won't thicken up as much, but you can cook it in the slow cooker. Cook up to the point you bring the curry to the boil, then place in the slow cooker and cook for 4-5 hours on high or 7-8 hours on low. If you want to thicken the sauce more, stir in a little cornstarch slurry at the end (2 tbsp cornflour (cornstarch) mixed with 6 tbsp of cold water).