Which technique is not associated with curling hair?

The technique associated with curling hair involves methods that create waves or curls in the hair. Straightening is not related to curling; rather, it works to flatten and smooth the hair. Techniques like thermal designing, finger waving, and the use of curling irons specifically focus on creating curls and waves.

Thermal designing typically uses heat to create curls, while finger waving involves shaping wet hair into waves using the fingers. Curling irons are directly designed for the purpose of curling hair by wrapping sections around a heated barrel. Since straightening fundamentally alters the hair's structure to achieve a smooth, sleek look, it falls outside the techniques associated with curling, making it the correct answer to the question.