Upon clicking the "Create Box" button, the script checks if a composition and at least one text layer are selected. It then creates a shape layer named "Text Box" and adds a rectangle shape to it. The shape layer's properties (Scale, Position, Rotation, Anchor Point) can be linked to the selected text layer (or to the layer that is above it) based on the user's checkbox selections. The script also allows centring the anchor point of the text layer.