1. Cut your potato in half lengthwise, and set the flat sides down on the chopping board or working surface.
2. Slice both halves of the potatoes lengthwise and then flatten them out your surface.
3. Now chop them again, into french fry-like shapes.
4. Once that's done, separate them into two equal sized piles of sliced potatoes, and turn 90 degrees.
5. Now, chop the potatoes again straight down to make diced potatoes.
Look at you go! Now you're ready to core and slice up a tomato, professional chef-style.