Which technique involves using a piece of foil or thermal strip to hold lightener or color?

The technique that involves using a piece of foil or thermal strip to hold lightener or color is effectively described by the choice that combines both weaving and slicing. In this method, sections of hair are either woven or sliced, and then the lightener or color is applied. The foil or thermal strip acts as a barrier, allowing the hair to develop more effectively while preventing the color from bleeding into other sections.

Using foil helps to isolate each section of hair, which is essential for achieving precise and controlled results, especially when working with multiple colors or lightening hair. This technique enhances the brightness of the highlights while maintaining the integrity of the base color.

In contrast, techniques like balayage involve freehand application without foil, which can lead to a more blended, natural look but doesn't utilize a foil or strip for color retention or development. Similarly, ombre typically describes a gradient effect from dark to light and does not specifically involve foils, focusing instead on the gradual transition. Thus, the combined technique of weaving and slicing with the use of foil is the correct choice when discussing controlled color application methods in hairstyling.