You can use any seasoning on the chicken you want, but I would shy away from anything heavy on salt (you already brined it it) and sugar (it'll burn over the high grill heat).
Stir in the salt, sugar, garlic, sage, basil, peppercorns and the bay leaf. Bring to a simmer and continue simmering, stirring often, for about 20 minutes. Make sure that the salt and sugar are completely dissolved.
Remove pot from heat, cover and let cool completely, at least 2 hours.
For the chicken
Add the chicken to the brine and transfer the pot to the fridge for 2 hours and up to 4 hours maximum.
If cooking the chicken on cedar planks, begin soaking them in water 30 minutes before using.
Fire up your grill for direct and indirect cooking.
If using planks, char the planks over direct heat on both sides first. Add the chicken and move the planks to indirect heat and continue cooking, 30-45 minutes or until the chicken measures 165 F with a thermometer.
Place chicken directly on the grates over high heat and sear on both sides, 2-3 minutes per side. Move the planks to indirect heat and continue cooking, 30-45 minutes or until the chicken measures 165 F with a thermometer.