Wood radical — a 桩 is a wooden stake or pile driven into the ground (foundation pile, hitching post). The radical anchors the literal sense 'stake of timber'. Same family: 板 plank, 柱 pillar, 椅 chair, 桶 bucket, 棍 stick.
Phonetic — 庄 zhuāng matches 桩 zhuāng exactly. 庄 historically meant a manorial village; here it functions purely as a sound element. Same phonetic appears in 装 install, 妆 makeup, 壮 robust, 状 condition — all zhuāng family.
