Whisk the water and xanthan gum in a medium saucepan over medium heat until smooth and forms a gel. Add the remaining ingredients and stir to fully combine. Continue stirring constantly until the mixture come to a low boil. Reduce the heat to medium low.
Simmer 3 to 5 minutes stirring frequently until the mixture is slightly thickened. Remove the saucepan from the heat and adjust the flavors if needed to your taste. Allow the sauce to cool in the pan for 10 minutes . It will continue to thicken up as it cools.
Pour the sauce into a mason jar or an airtight container. Use immediately in any recipe that requires Korean barbecue sauce or store in the refrigerator up to 1 week.