In a small bowl add the salt, sugar, garlic, rosemary, and thyme. Pour over the boiling water and stir until the salt and sugar are dissolved. Leave to rest and cool while preparing the cooler and turkey.
Using dishwashing liquid (not a harsh chemical or bleach), clean the cooler. If hot water is used ensure that it is cooled with some ice before adding the brine.
Remove the turkey from its packaging; remove the giblets and trim any excess fat. Rinse under water then place in the clean cooler.
Pour the prepared brine concentrate over the turkey.
Add the cold water to dilute the brine, stirring to ensure it is evenly distributed. If you are concerned that the brine will not remain cold, add some ice cubes.