A word or expression to describe a person who tells someone else how to do their work

Solution 1:

Farlex has backseat driver.

1. A passenger in a vehicle (not necessarily in the backseat) who attempts to instruct the driver or criticize their driving skills.
2. By extension, it also means someone who tries to establish and maintain control over every situation.

Lexico supports this with

back-seat driver
_NOUN

1.1 A person who is eager to give advice about something for which they are not responsible.

She failed to appreciate that the term ‘back-seat driver’, in most people's eyes, was pejorative: she thought it merely indicated helpfulness, whereas others saw it as meddling and controlling.