Written communication is better for specs on work to be done. It can be enhanced with diagrams, images, mockups, etc. Bulleted lists are effective for listing out acceptance criteria and details they need to be aware of.
But there is also a human side to it. When I led offshore teams (from India and Mexico), I worked hard to get to know them, which included open discussion of our communication. Sometimes it was just talking to them often enough that we knew each other's accents. Especially for coworkers in India, we all knew English well, but spoke it quite differently. They had a hard time understanding my American accent, so I'd deliberately slow down when talking. I also would stop the conversation and make sure that if words were not understood, we had a culture of just saying so and trying again.
We still had times when we struggled to understand each other, but they trusted that I didn't let that get in the way of how we worked together. They knew that communication problems were something we could work at, and laugh at, and was not going to be looked at as a failure.
It isn't all that different than any other communication concerns within a team - the more you build trust, the better communication gets.