Mix yeast, sugar and warm water together in a bowl; set aside for 5 minutes.
Combine flour and salt together in a larger bowl; make a well in the centre and pour in yeast mixture and 4 tablespoons olive oil. Work quickly to combine and form into a dough; turn out onto a clean surface and knead until smooth. Return dough to the bowl; cover with a clean drying cloth and let rise in a warm place for about 1 hour, or until doubled in size.
Grease a 30x20cm rectangular baking tray.
Knock back dough and knead lightly; roll dough out to 2cm thick and arrange in prepared baking tin. Set dough aside in a warm place to rise for a second time, about 30 minutes.
Preheat oven to 200 C / Gas 6.
With the handle of a wooden spoon make deep depressions into the dough at 5cm intervals. Drizzle a further 2 tablespoons of olive oil over the surface and scatter on some coarse sea salt.
Bake bread in preheated oven for 20 to 30 minutes, until well risen and golden.