Whether or not you chop your spinach leaves is totally up to you. Some recipes call for cutting spinach leaves off of the stems, but you can also keep it simple and use pre-washed spinach leaves from a bag.  The smaller you chop your leaves, the more dressing they will soak up and the quicker they will become soggy so I prefer to keep my leaves whole. Make sure to serve your salad in a large bowl so that it is easy to mix the toppings and dressing together without making a mess!