Combine marshmallow root and water in a small pot and simmer over medium-low heat for 15-30 minutes.  This cooking time will allow the mucilage to release. The longer you let it simmer the thicker the mixture will be.  If the mixture gets too thick, you can always dilute it with extra water. 

Remove pot from heat and allow mixture to cool.  Strain the liquid from the marshmallow root using a fine mesh strainer.  

Once the mixture is cooled and the liquid is separated, add in remaining ingredients, and stir to combine.  Transfer to a spray bottle and store at room temperature for up to 3 months.