The interlacing technique has a long history of use as a means of creative expression and persists in modern society to satisfy the individual pursuit of pastimes. This method has the developmental potential to create new trends in the future. Interlacing techniques (e.g., basketry, plaiting, braiding, and knotting) are closely related to plastic arts fields, architecture, art, and industrial design where the various interlacing practices are applied. This research uses case analysis to study the types of expression found in the formative art field wherein the interlacing technique is applied. Results reveal several expressions, including optical illusion visual type, relief surface type, porous perspective type, and object borrowing type, all of which appeared in fashion bags. The aesthetic formativeness, which appeared in the fashion bags that applied interlacing techniques, was then classified according to geometric formative beauty in a process based on rules and order. Nature-friendly formative beauty reflecting handicraft locality and omnidirectional formative beauty by disordered deconstruction and heterogeneous combination were determined. The use of interlacing techniques that show creative, unique combinations and variations is expected to inspire the development and application of bag design that suits individual and original modern fashion trends. One limitation of this thesis is that it only studied cases appearing in modern fashion bags.