WHOLE CHARACTER
参cān, shēn, cēn, sān
to join; to take part in (参加, 参与); to refer to (参考, 参照); to look in on (a superior) (参见)
参 joins in — take part, consult; read shēn for ginseng, cēn for uneven.
The header says the formation was originally 形声 for the older 參; the simplified stacked pieces are shown visually without a sound rule.
TOP PIECE (厶)
厶sī
private (an old graph)
An old bound piece used inside several characters; not a standalone modern word.
In 参: top piece (厶) A reduced top piece; no role is claimed.
MIDDLE PIECE (大)
大dà
big; large
A standalone character; kept separate from the unclaimed visual role in 参 and the base-figure role in 天.
In 参: middle piece (大) Shown as the middle piece; no role is claimed.
BOTTOM STRIPE PIECE (彡)
彡shān
hair; the three-stripe radical
The stripe radical; the shade lines in 影's classic account.
In 参: bottom stripe piece (彡) The three-stripe piece at the bottom.