What technique is commonly used to achieve volume at the roots of hair?

Teasing is a technique specifically designed to add volume at the roots of the hair. It involves using a fine-toothed comb to backcomb sections of hair, which creates a cushion of hair fibers at the base. This not only lifts the hair away from the scalp but also creates a fuller appearance throughout. Teasing is often used in styling for special occasions or when extra volume is desired, making it a popular method among hairstylists.

The other options, while they may have their own specific uses in hair styling, do not effectively provide the same level of root volume. Flat ironing is typically used to create straight, sleek styles and can actually flatten the hair. Smoothing generally focuses on eliminating frizz and creating a smooth finish, which again can lead to a sleeker look rather than adding volume. Braiding can add texture or interest to a hairstyle but does not inherently lift the roots or enhance volume.