In a medium-large bowl, combine flour, salt, and instant yeast. Stir well. Add the warm water. Using a wooden spoon or a rubber spatula, mix until all of the flour is well incorporated (there should be no small pockets of flour. Cover the bowl with a plastic wrap and tea towel and sit a warm part of your kitchen or house for 2 hours.
Lightly oil a large focaccia tray—place your risen dough in the oiled pan (35x24x5 tray), turning to coat with oil. spread out, gently, so that dough covers the entire tin.
Cover the pan tightly with plastic wrap and allow the dough to rest and rise for another 2 hours (it may take as long as 3 hours, depending on the warmth of your kitchen). The dough should cover most of the pan.
Preheat oven to 180˚C with a rack positioned in the centre of the oven. Drizzle another tablespoon of oil over each round of dough. With oiled fingers, using both hands, press straight down and create deep dimples that go all the way through the dough (in other words, you'll actually be making deep holes.) If necessary, gently stretch the dough as you dimple to allow the dough to fill the pan.
Sprinkle tops with fresh herbs and arrange your chopped, seasonal veg across the top of the focaccia.
Transfer the pan to the oven and bake for 22 to 28 minutes, until the tops are golden and the undersides are crisp. Remove pan from the oven. With a metal spatula remove bread from the pans and transfer to a cooling rack.
Serve straight away, or freeze portions for up to three months.