Ask HN: How do you improve and encourage communication efficiency while remote?

What's the best way to improve employee communication efficiency? As much as I love slack, I find it much more productive to be able to walk over to someone's desk and spend a couple of minutes discussing an issue or solution instead of having to type up a message, clarify the message, and any questions that pop up from confusion etc. etc.

Slack does have a call feature but I find it somewhat lacking because people might not be at their desk, have their speakers turned off, have notifications turned off, not have Slack open, not have their mic or video set up correctly etc. etc.

Are there any tools, policies, or guidelines that your company has implemented to help communication efficiency?