What is the Sharia ruling on a woman working in interior design, which entails interaction with engineers?

A woman is permitted to interact with non-mahram (definition) men in her company or workplace, provided she adheres to the Sharia (definition) guidelines, such as avoiding private seclusion (khalwa (definition)), suspicious mixing, and speaking in a soft, alluring manner. She must also maintain her hijab (definition) and lower her gaze. If she can adhere to these guidelines, then there is no impediment to establishing a company and employing men or women. Nevertheless, the preferable and safer option—unless there is an urgent need to work—is to generally avoid mixed environments, even if the mixing is not suspicious.