How do I make an decoction? The usual recipe is 1 tbsp. of herb's bark or root to 1 quart of boiling water. The liquid is boiled (covered) until half of it has evaporated. It is then strained and placed in the refrigerator until needed. When preparing a decoction dosage, make sure to add 1-3 tbsp.(according to recipe) to a cup of warm water before drinking. I usually do not use decoctions myself, I prefer infusions. They are much simpler.