In a separate bowl, combine 1/2 cup water and use the end of a toothpick or lollipop stick to dot the blue food coloring and mix it into the water. Then do the same for the yellow. I like to use a mix of yellow and blue so I can choose my green color and not have to go with a dark green.
Mix in 5-7 drop of your essential oil to your water and stir.
Add in the two tablespoons of water at a time to your cornstarch. Continue to mix to the colors disperse and clumps begin to form. Please note that this amount of water will NOT be enough to make the paste you are after. It is however a starting point so you can carefully ration water in and form your paste. I used about 1/2 cup exactly.
Continue adding a few drops of water at a time, mixing well as you do. Once you have a thick paste it will be hard to mix but scoop and transfer the mixture to your square silicone mold. Smooth the mixture out flat using your finger tip.
Freeze the contents for 1 hour or until the mixture is set.