flag
旂 centers on a flag, specifically a banner or pennant used as a symbol or signal.
旂 combines 方 (direction/square) with 斤 (axe), likely representing a flag or banner with a pole and a cloth or emblem. The exact historical development is uncertain, but it is associated with flags in ancient texts.
The left side 方 suggests a square banner, and the right side 斤 looks like an axe on a pole. Imagine a flag with an axe emblem flying from a square banner.
For キ, picture a key flag that unlocks a gate: key -> キ, and the flag signals the entrance.