Chop up the tomatoes (optional), mozzarella, and basil (optional).
Place the ingredients onto a plate in layers (mozzarella, tomato, basil) or put them into a bowl and toss with some salt, pepper (optional), and olive oil or balsamic reduction.
Notes
If you want to make this recipe ahead then it is best to avoid cutting basil and cherry tomatoes. In that case, it is easier to just toss the ingredients in a bowl instead of layering them onto a flat plate. Balsamic vinegar or reduction is not originally a part of the dish and overpowers the ingredients' natural flavors. However, it is popular to add balsamic reduction to this salad, so you can try it and see if you like it!