两手空空

• 一(one; top)RADICAL
• 冂(frame; border; surround)ASSOCIATIVE
• 从(two people walking together)ASSOCIATIVE

Two people standing together in a frame symbolize the number two, a pair.

• 手(hand (pictographic))ASSOCIATIVE

The character 手 mimics the image of a hand with five fingers spread out.

• 穴(row; gap)RADICAL
• 工(craftsman; work)PHONETIC

An empty cave with nothing inside is just hollow space.