肪 almost never appears alone in modern Chinese - it lives inside the compound 脂肪 ('fat'). Knowing 肪 mostly helps you recognize 脂肪 and related medical terms.
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The 月 (flesh-meat) radical signals body tissue, and 方 gives the sound. Many flesh-radical characters work this way: 肝 (liver), 肺 (lungs), 肠 (intestine).
⺼ is the meat-flesh radical, visually identical to 月 (moon) but historically distinct. It marks body parts and animal substances: fat, organs, limbs. 肪 sits with 脂 fat, 肉 flesh, 肝 liver, 胸 chest, 肚 belly - all anatomical chars sharing this radical.
方 supplies the sound: fāng to fáng, tone shift only. It carries no clear semantic load here, but its rectangular shape can serve as a quick memory hook - slabs of fat are dense and blocky. Same phonetic series: 房 house, 防 guard, 妨 hinder.
