I don't think it's too complicated, especially if you start in a culture where people don't job-hop all the time. But, you have to make it your priority, which means:
* pay them more than competitors, pay them more than if they changed jobs
* actually treat them well, which includes listening to and acting on their feedback
* celebrate people with long tenure
* give them options to grow inside the company
* don't just hire fresh graduates, a 40yo might be tired of job-hopping and still has 20+ years of employment in them
* give them long-term incentives, like stock options
That doesn't sound like an easy hack at all, but I can appreciate the value of achieving it. Are there any good books or studies on this subject?