Lightly grease a large plastic container (I used a metal mixing bowl) with olive oil. Line two large baking sheets with greaseproof baking paper.
Put 500g strong white flour, 10g salt and a 7g sachet of instant yeast into the bowl of a freestanding electric mixer fitted with a dough hook. (Don’t put the salt directly on top of the yeast). Add 2 tbsp olive oil and three-quarters of the water (265 ml) and start to mix on a low speed. As the dough starts to come together, add the remaining water very slowly, then mix for eight minutes on a medium speed. Add 2 tsp chopped sage and 2 tsp chopped thyme and mix for a further minute. When ready, the dough will be very elastic and you should be able to stretch it away from the bowl.
Tip the dough into the oiled container/bowl. Cover and leave to rise until at least doubled in size – about an hour (I left it an hour and 15 minutes and it was definitely more than double by then). The dough should be bouncy and shiny.
Dust the work surface with flour. Tip out the dough. It'll probably be quite loose - it's meant to be like this. Divide the dough in half.
Lift each piece of dough onto the prepared baking sheets and spread out into flat ovals. Make two cuts in a line down the middle of the dough with a gap between them (see photo). Paul Hollywood says to use a pizza cutter. I couldn't find ours so I used a sharp knife, but it was pretty tricky as the dough just stuck to the knife. Then make 12 diagonal cuts in the dough, six on either side of the central cuts, forming a leaf design, then stretch the dough out slightly to emphasise the holes.
Place the baking sheets inside large plastic bags and leave to prove in a warm place for 20 minutes. (I didn't have any large plastic bags so I left it to prove in the open) Preheat the oven to 220°C/200°C Fan/gas mark 7.
Drizzle over a little olive oil. Sprinkle over the oregano and bake for 15–20 minutes, or until the fougasse sounds hollow when tapped on the base (they took 25 minutes in my oven). Remove from the oven and while still hot, brush with more olive oil and sprinkle with the sea salt.