The word 搔首弄姿 is formed by directly combining two verb-object phrases: 搔首 (scratching the head) and 弄姿 (fiddling with one's posture). These phrases are placed side-by-side in a parallel structure, with each character retaining its literal meaning, 搔 (to scratch), 首 (head), 弄 (to play with or adjust), and 姿 (posture), to collectively depict actions often associated with flirtatious or coquettish demeanor.