Flannel Sheets Basic Exclusive report by Felix Goh So, what is flannel made of? Flannel is actually a type of loosely woven fabric, made of wool and sometimes even boasts a blend of wool, cotton or wool and synthetic fibres which could be polyester. Flannel types vary in weight and the smoothness and fineness of texture. Some people have a knack for sleeping on the flannel sheets year-round. If you are on t ...