When cutting sweet potatoes or any “wobbly vegetable” having the right knife and bringing the food to a flat surface are the keys to success.
Because sweet potatoes are dense, you’ll want a knife that is big enough and sharp enough to make a smooth cut, like a 7-5/8" Petite Chef knife. After peeling the potato, find a place on the potato where it can rest on the cutting board without too much roll or wobble. Then, after that first cut, lay pieces flat on the board for safe, even slicing and dicing.
Whether you’re making sweet potato fries or dicing them for roasting, make sure you cut the potato to a uniform size so all the pieces cook evenly.