https://www.thespruceeats.com/what-is-xanthan-gum-p2-1000974#how-to-use-xanthan-gum-in-cooking
No heating or cooling is needed for xanthan gum to form a gel—it does so as soon as it is in contact with a liquid. Acid and heat don't affect it, so it can be used in a wide variety of sauces and juices.
To use xanthan gum in recipes, use about 1/8 teaspoon per cup of liquid and combine these in a blender, not by hand. It will "gum" almost instantly and form clumps if not constantly in motion while it is being incorporated into the liquid.
For sauces, blending the xanthan gum first with a bit of oil before adding the soymilk or rice milk produces the best taste and texture, as this gives the sauce richness and depth that would normally be achieved by cream, butter or eggs. The more xanthan gum is used in a liquid the thicker it will become.