You walk really slowly.

Literal

Walking-way [subject-が] very slow is-ね.

歩き方 is 'the way of walking,' 'manner of walking' — the [verb stem]+方 nominalization. Here as the subject of a descriptive predicate (ゆっくり as a な-adjective/adverb). ね is the sentence-final agreement/softening particle, making the observation gentler, 'you know?'