How do you optimize your employees or work force to increase productivity?

Productivity is fundamentally about process.  Improve the process, and you'll improve productivity.

In other to improve the process, it is usually helpful to understand the current process: not what is supposed to happen, but what actually happens.

Sometimes, quite small changes can have quite bit effects.

It is always helpful to consider "What step in the process is the bottleneck: where is production slowest or most expensive?"   Identify that step and improve it.  Repeat.  Repeat.  Repeat.