Mix the flour in with the yeast and salt in a large mixing bowl
Mix in the warm water until fully incorporated and then knead in the 2 tbsp of olive oil
If kneading by hand: flour your work surface and scrape the dough out onto the surface. Knead for 1 to 2 minutes, but be careful not to over-knead. The dough will be sticky but don't be tempted to add more flour
If kneading in a standalone mixer: let the machine knead the dough for 1 minute
Place the dough into a well-greased (oiled) bowl and cover it with a damp tea towel. Leave in a warm place to rise for around 1 hour (or until double in size)
Scape your dough out of the bowl into an oiled baking tray (about the size of a large brownie tray) and push down on the dough using your fingertips, until all the air has been released
Using your hands, pull the dough out to the sides, so it fills the whole tray
Sprinkle the other 2 tbsp of oil on top, along with a large pinch of sea salt flakes, and the leaves from the rosemary sprig.
Push the cherry tomato halves into the dough so that the dough comes up over the sides slightly. I like to keep the inside of the tomato half pointing up as it looks prettier!
Re-cover the dough with the damp tea towel and leave to rise again, until the dough is reaching the top of the tray (nearly doubled in size)
Preheat your oven to 220ºC fan
Place the tray into the oven and cook for about 10 minutes and then check on the bread. If it is browning too quickly, reduce the temperature to around 180ºC fan. Cook for a further 15 minutes (or until the bread makes a hollow noise when you tap on it)
Leave the focaccia to cool for a while before pushing it out of the tray. Serve warm with your favourite dips or pasta dish