Sift the powdered sugar through a fine-mesh sieve into a large mixing bowl. This step is crucial for lump-free, smooth icing.

In a separate small bowl, whisk together 1/4 cup of milk (or water), light corn syrup, vanilla extract, and almond extract (if using) until well combined.

Pour the wet ingredient mixture into the sifted powdered sugar. Using an electric hand mixer on low speed, begin mixing until just combined. Gradually increase speed to medium-high and beat for 2-3 minutes until the icing is smooth, creamy, and free of lumps. Scrape down the sides of the bowl as needed.

The initial consistency will be quite thick, suitable for outlining. For a thinner 'flooding' consistency, add additional milk or water 1 teaspoon at a time, mixing well after each addition, until the desired flow is achieved. A good 'flood' consistency will smoothly settle back into itself within 10-15 seconds after a line is drawn through it with a spoon.

If coloring, divide the icing into separate bowls before adding gel food coloring. Start with a small amount of coloring and gradually add more until you reach your desired shade, mixing thoroughly each time.

Transfer the icing to piping bags or squeeze bottles for decorating. Outline your cookies with the thicker consistency icing, then flood the outlined area with the thinner consistency. Use a toothpick to spread the flood icing to the edges and pop any air bubbles.

Allow decorated cookies to dry completely on a wire rack at room temperature. Thin layers will dry within 4-6 hours, while thicker layers or multiple colors may take 12-24 hours. Ensure cookies are fully dry before stacking.