Add water, yeast and sugar to a large mixing bowl, stirring to combine.
Mix in 1/4 cup olive oil.
Add 2 cups of flour with 1 teaspoon of kosher salt. Mix together with a dough whisk or wooden spoon.
Continue adding flour 1/2 cup at a time until dough comes together into a ball and pulls away from the sides of the bowl.
Flour a clean surface or large cutting board.
Pour the dough onto the floured surface and knead by folding the dough over onto itself for 3 - 5 minutes or until dough is no longer sticky.
Flour the board again and use a rolling pin to make an 8 x 10 x 1/4 inch thick rectangle.
Carefully place the dough onto a piece of parchment paper on a flat cookie sheet, without a rim or a pizza peel.
Mix 2 tablespoons of olive oil with the minced garlic.
Use the tip of your index finger or the rounded end of a wooden spoon to make indentions all over the dough.
Brush the garlic and olive oil all over the dough.
Sprinkle with rosemary, dried onion flakes, flake salt and chile flakes.
Prepare a grill fire to 325° using a pizza stone. (400° if using a pellet grill or gas grill.)
Sprinkle the pizza stone with a light dusting of cornmeal.
Slide the focaccia dough onto the pizza stone with the parchment paper.
Close the grill and cook 5 minutes. Pull the parchment paper out from the dough and turn the focaccia 90 degrees. Continue cooking, turning every 5 minutes until the bread is golden brown on the bottom and the bread is cooked through, about 15- 20 minutes.
Remove from the grill to a cutting board. Slice with a pizza cutter and serve immediately.