maple tree
槭 centers on the maple tree, a specific type of tree known for its distinctive leaves.
槭 combines 木 (tree) with 戚, which likely contributes the sound. The character was created to name the maple tree specifically.
The tree radical 木 stands beside 戚, a shape that resembles a person under a roof with a weapon. Picture a maple tree growing beside an old house, its leaves turning red like a warning flag.
For セキ, imagine a maple tree with a red leaf stuck to a stone seat: seki -> セキ, and the leaf marks the spot.
trident maple (Acer buergerianum)