桌

Bottom indexing wood radical - marks the table's material as wooden furniture. Added later to disambiguate the original 卓 (tall, standing) into the specific 'tall wooden object you sit at'. Same radical anchors the household-furniture family: 椅 (chair), 床 (bed), 柜 (cabinet), 板 (board).

Top component supplies the sound (exact match: zhuō) and a strong semantic echo. 卓 means 'tall, upright, standing out' - a fitting picture of a table standing on its legs. Note the slight contraction: standalone 卓 has 8 strokes, here compressed to 6 in the top position. 桌 was originally written as just 卓; the wood radical was added later to specify the material. Same phonetic in 倬 (zhuō, conspicuous).