When cooking them on the hob, I soak them overnight then do the 'boil rapidly then cook for 1.5 hours' thing. But how do you do them in a slow cooker? Presumably you still need to boil rapidly and get the scum off, but do you then put them straight into the slow-cooker instead of simmering for 1.5 hours? Or do you still simmer for 1.5 hours and then put them in the slow cooker? Thanks!