Yes, slow cookers, if being used properly, are entirely safe to leave cooking on the countertop unattended. u003cbr/u003eu003cbr/u003eu003cstrongu003eu003cemu003e3 tips if you’re planning to leave it on all day:u003c/emu003eu003c/strongu003eu003cbr/u003eu003cbr/u003e1. Set it to low.u003cbr/u003e2. Place the slow cooker on a heatproof flat surface away from the wall.u003cbr/u003e3. Add enough ingredients. You should fill the slow cooker ½ - ¾ the way full. If you don’t fill it enough, you can run the risk of the recipe burning.