After washing the celery throughly dry the stalks with a tea towel or paper towels. Then cut about an inch off both the top and the bottom of the celery stalk. You can save these pieces for soup stock or to flavor stews. Just place in a plastic bag and put in your freezer.
Then cut the celery stalk into three pieces like this.
Then cut each of those pieces into four pieces length wise, like this.
Bunch those four pieces together and cut across them into small, medium, or large dices depending upon what the recipe calls for.
Do that till everything is diced. There you have your dice …..easy peasy.