Your employee misinterpreted your email. You believe the channel was the problem and:

Scheduling a meeting to discuss the miscommunication is the most effective approach in this scenario. This option allows for real-time dialogue, enabling both you and your employee to clarify misunderstandings directly and foster a clearer understanding of the expectations and instructions.

By discussing the issue face-to-face or via a virtual meeting, you can gauge the employee's interpretation of the initial email and provide an opportunity for them to ask questions. This interaction not only helps resolve the current miscommunication but also strengthens the working relationship, promotes a collaborative environment, and can prevent similar issues from occurring in the future.

A more detailed email might not address the underlying miscommunication effectively, as it lacks the personal interaction that can clarify nuances and tone. Reprimanding the employee may create a negative atmosphere and discourage open communication, while closely supervising the project may indicate a lack of trust instead of empowering the employee to learn from the experience.