You should slice off a small bit of potato from the side before making your actual knife cuts to create a flat, stable surface. This slice provides stability to the potato, preventing it from rolling or shifting on the cutting board, which makes cutting safer and more controlled. Having a flat side down allows you to make more even, precise cuts and reduces the risk of knife slips and accidents while preparing the potato. This technique is especially important because potatoes are often rounded and uneven, which can make them unstable before slicing a flat edge.