20 minutes before the food goes in. i’m primarily round the house all day so i don’t need a digital timer to turn it on or off. you might be totally different and need a slow cooker big enough to double as a baby’s bath with a control panel that could land a plane. thinking about how the slow cooker will fit your life is the crucial bit before you start shopping so you don’t buy a white elephant.
no matter what your needs are, consider a couple of other things. an oval slow cooker is always easier to fit stuff into than a round one. you must never ever fill 