作 puts a person 亻 beside 乍, which in oracle script showed a collar being cut and sewn — the moment of making. A person in the act of creation: to do, to make.
作 is the maker's verb: 工作 (work), 作家 (writer — one who makes with 家, home/master), 作业 (homework, every student's burden). Note the twin: 做 also means 'do' — roughly, 作 leans abstract and literary (作梦, 作曲) while 做 leans hands-on (做饭, 做事), and 工作 always uses 作. Even native speakers pause over the pair.
A person 亻 suddenly 乍 springing into action — to DO, to MAKE.
作家 'one who makes' is a writer — the same maker-root as English 'poet', from Greek poiētēs, 'maker'.