In a microwave safe bowl, combine the corn syrup with the corn starch. Whisk until the corn starch is dissolved.
Whisk in the cold water.
If using flavor, add in 1/4 teaspoon of extract such as vanilla or almond extract. Keep in mind, it is better to use clear extract if you don't want a tinted piping gel. *I omitted flavor since piping gel sits on top of my vanilla buttercream.
Microwave on high until the mixture is boiling and turns clear. This only took about a minute and 15 seconds for me.
Whisk the homemade piping gel until the bubbles are gone.
Allow the mixture to cool for about 5 minutes.
Stir in the gel food color if adding color and then pour the mixture into a piping bag or icing bottle. Use immediately.