Making licorice root syrup or extract
Licorice root can be simply simmered in water to make a basic licorice extract, but it's quite weak, and not very "zesty"

Modern commercial licorice root extraction uses ethanol under pressure and heat, and a form of ultrasonic "distillation". None of this is very likely in the home kitchen :-(

You could try using a water and ethanol solution (say basic vodka), in a closed pot, and simmer below the boiling point of ethanol 78°C (172°F). Do this outside and wear protective face wear in case of a flash fire

Here is an old patent which may provide more clues http://www.google.com/patents/US3131175