Peel the carrots and halve them crosswise so they’re easier to handle. Slice a thin strip off the carrot half to create a flat surface. Turn the carrot half onto the flat surface so it’s stable and doesn’t roll around. Now carefully slice the carrot piece into planks about 1/8-in. wide.
Stack 3 or 4 carrot planks on top of each other. Now slice the stack of carrot planks lengthwise to make matchstick shapes.
Finally, gather the sticks into a bundle on the cutting board. Holding the bundle together with your left hand if you’re right-handed, or your right hand if you’re left-handed, cut the carrot matchsticks crosswise into cubes. The closer together you make the cuts, the smaller the diced carrots will be.