Mix together all the flour, the salt, the yeast and the lemon juice with the water in a food processor using a dough hook (or knead by hand). When the dough is thoroughly mixed, add the olive oil. Use the Instant Read Digital Thermometer to check whether the dough has a temperature of 25°C. If the temperature is too low, continue to knead for a bit longer.
Flatten out the dough, fold the edges towards the middle and brush with olive oil. Turn the dough over so that the fold is facing downwards and brush the other side with olive oil. Fold the edges down to create a nice round ball of dough. Grease the Cast Iron Skillet with olive oil, place the ball of dough in the skillet and flatten the dough. Leave to rise at room temperature for 2 hours. Press the dough down a bit more every half hour so that by the end of the rising time it is spread out over the skillet. Brush the dough with extra olive oil if it becomes dry as it rises.
Ignite the charcoal in the Big Green Egg about 20 minutes before the end of the rising time. Heat the EGG, with the convEGGtor, the grid and on top of that the Flat Baking Stone, to a temperature of 230°C.
Moisten your fingers with olive oil and make dents here and there in the top of the focaccia dough. Sprinkle the dough with the coarse sea salt. Put the Cast Iron Skillet on the Flat Baking Stone, close the lid of the EGG and bake the focaccia for approximately 35 minutes until golden brown and done.
Remove the Cast Iron Skillet from the EGG using the EGGmitt. Remove the focaccia from the skillet and leave to cool.