Duofold Women's Mid Weight Wicking Thermal Leggings are another top-rated option for women's flannel base layer bottoms. These leggings are made from a blend of polyester and spandex, which provides a comfortable and stretchy fit. The fabric is designed to wick away moisture, keeping you dry and comfortable during physical activities. The leggings have a mid-weight thickness, making them suitable for both cold and mild weather. Whether you're going for a run or just running errands, these base layer bottoms will keep you warm and comfortable.