Right
欠 supplies the sound — qiàn drifted to kǎn through a regular Old Chinese k/q alternation.
欠 itself depicts a person leaning over with mouth open (yawning, sighing, owing). Same phonetic in
砍's near-twin
坎 kǎn (pit),
嵌 qiàn (inlay). Pure phonetic loan; the 'yawn' meaning contributes nothing semantic.