Cookie Periodic Table aka. "The Periodic Table of Aliments"

Step 6 Apply toppings to the cookie rectangles

Take each of the baked cookie rectangles and spoon a generous quantity of icing onto its center. Work to spread the icing from the middle out, being careful not to scrape the surface and pull up crumbs. Once the cookie square is completely covered let it sit until the topping hardens (should be 2-5 hours depending on how liquid your topping was, how warm the dough was, and the temperature of your kitchen).

If you have problems leaving delicate projects out without them being disturbed by cats or other household pests, then carefully use the parchment paper (still under the cookie rectangle) to slide the iced cookie onto a hard flat surface such as a cutting board and refrigerate until the topping is set. Keep the cookie as supported and flat as possible while moving so that it doesn't bend or crack.