Making the filo dough
Place the flour into a bowl with the salt. Make a well in the centre and pour in the olive oil and vinegar. (The vinegar here helps with the flakiness of the pastry.) Start mixing, either with a spoor or your hands, adding the warm water until it resembles a soft dough. You may need more water, or you may not need all this. Tip the dough onto a floured surface and knead lightly until it is smooth, place back into the bowl and cover with a tea towel, allow to rest while you make the filling.
Making the filling
Heat the olive oil in a frying pan and add the sliced leeks and onions, sauté until soft and golden.
Remove from the heat and place into a large bowl. Add the chopped spinach, fennel, mint, parsley and oregano, mix to combine. Crumble in the feta and using your hands mix all the ingredients. Check for seasoning as it may not need much salt because the feta is salty.
Making the pie
Preheat the oven at 180 degrees C.
Transfer the filo dough onto a surface that has been dusted with cornflour. Divide the dough into 6 balls.
Brush a 36 cms round baking tray with olive oil.
Take one ball of dough and roll out into a dinner size plate round. Brush with some olive oil and put aside. Roll out another piece of dough to the same size and place onto the oiled piece, brush with oil again and repeat with another piece of dough. You will have three sheets that have been oiled in between. Roll this out now to the size of your baking dish making sure it is enough to cover the sides as well.
Pour the filling onto the dough and spread evenly.
Repeat with the other 3 balls of dough and this time roll out more so it is ruffled and not smooth on top. When you place this layer of dough over the filling make sure the edges are neat by pinching them all the way around. Brush with olive oil and sprinkle with a little cold water.
Bake for about 1 hour or until it is golden and crisp. Sprinkle with a little more cold water when it is cooked straight out of the oven. Allow to cool, cut into pieces and serve.
Serve warm or cool.