Make the Dough: Add warm water and to a large mixing bowl (or your stand mixer bowl) along with yeast and sugar. Use a fork to mix, then rest for about 10-15 minutes so the yeast can activate. It should look foamy with little bubbles.
Attach a dough hook onto electric mixer and slowly add in the flour, salt and olive oil. Continue mixing until just combined and a ball of dough forms. Turn dough onto a lightly floured surface and knead for a few minutes until dough is smooth.To make by hand, add flour to yeast mixture in batches and mix with a spatula, then knead with your hands to form a cohesive mass, this could take up to 10 minutes. Let Dough Rise: Place dough into a lightly oiled bowl, turning so all sides are lightly covered with oil. Place a sheet of plastic wrap on top and let rise in a warm spot until doubled in size, about 1 ½ hours.
Prep the Tomatoes: While dough proofs, place sliced tomatoes on a paper towel lined plate and lightly sprinkle with salt to help draw out excess moisture. Use another sheet of paper towel to blot as needed.
Turn Dough onto Baking Sheet: Once focaccia has doubled in size, remove plastic wrap and gently punch down the dough to deflate. Oil a cookie sheet with 2-3 tablespoons of olive oil and turn the dough onto the sheet.
With oiled hands, gently stretch the dough so it reaches the edges of the cookie sheet. Use your fingers to press in deep dimples into the dough.
Garnish Dough: Add sliced tomatoes and garlic all over the top of the dough, gently pressing down into the dough. Sprinkle with chopped herbs and season with salt and remaining olive oil.
Let Dough Rise Again: Cover dough with plastic wrap and rise for another about 30 minutes.
Pre-Heat Oven: While dough proofs for a second time, pre-heat oven to 425 degrees Fahrenheit.
Bake: Bake focaccia for about 35-40 minutes or until the edges are golden brown.
Once done baking, remove from oven and allow to cool for at least 15 minutes before serving. Garnish with fresh basil leaves, if desired.