Which technique is effective for creating volume at the roots of hair?

Base curls are specifically designed to create volume at the roots of the hair. This technique involves wrapping sections of hair around a roller or curling tool at the base, while leaving the ends free to allow for lift. By focusing on the roots, base curls work to establish a solid foundation of volume, making the hair appear fuller and more voluminous.

In contrast, spiral curls are generally used for creating a more defined curl pattern rather than for adding root volume. Pin curls can also provide lift, but they are more versatile in terms of style and may not focus primarily on the root area as effectively as base curls do. Flat iron smoothing is primarily a technique for straightening hair and achieving a sleek finish, which does not contribute to creating volume at the roots. Thus, base curls stands out as the most effective method for achieving the desired volume at the roots.