Sprinkle the yeast over the water, if using active dry yeast and set aside a couple minutes while you measure other ingredients - with instant you can add it to the flour. Place the flour, salt (and yeast if using instant) in a stand mixer or medium bowl if mixing by hand. Mix the dry ingredients briefly then add the water. Mix to combine then knead for a few minutes - roughly 3 - 5 in mixer or 5 - 8 by hand. It will be sticky, but resist the temptation to add extra flour. Just work it and it will gradually become les sticky and just a bit tacky but very smooth.
Once kneaded, bring the dough into a ball, place in a clean, lightly oiled bowl, cover and ideally, place in the fridge overnight to rise slowly. Alternatively, leave to double in size, roughly 1 ½ to 2 hours at warm room temperature.
Prepare a 9 x 9in (23x23cm) baking pan/tin with parchment at least on bottom and two sides, if not all sides. Finely chop the rosemary.
If the dough rose in the fridge, take it out roughly 30 minutes before using to come to room temperature. Once the dough is ready/doubled, uncover and knock back the dough with your hands. Divide the dough in two and take one half and ease it out relatively thinly with your fingers to be roughly the size of the baking pan. Place in the pan and spread the dough to the edges, dimple the dough a little with your fingertips.
Top the dough with a little under half of the grapes, scattered relatively evenly and nestled into the dimples. It should look like quite a few but with some gaps in between. Sprinkle around half of the rosemary and drizzle over around half of the olive oil, both as evenly as you can over the top. Sprinkle over around half of the sugar, again as evenly as you can.
Stretch out the other half of the dough and place over the top of the grapes in the baking pan. Pinch together the edges of the dough to try to help the layers stick together. Dimple the dough again, though it will be tricky with the grapes underneath. Top with the rest of the grapes, rosemary, olive oil and sugar (for this layer I quite like the oil first, then grapes, but the order is not particularly important).
Once the bread is formed, preheat the oven to 375F/190C and let the bread sit as the oven warms. Then, bake for around 35 - 50 minutes, depending on your oven and pan, until the top of the bread is gently browned and the bread is cooked through. Allow to cool until at least just warm, or cool completely (it's delicious warm, but a bit easier to cut and eat once cool). Best eaten on day of baking.