Put all the ingredients for the filo in a large bowl and knead so that you make a ball.
Divide the dough into 13 balls (make the 3 that will go last on top a bit smaller and the 4 that will go to the bottom should be larger).
Cover them with a towel and then a small tray and set them aside for at least 2 hours (sometimes I make the dough in the evening and leave it overnight).
Chop the spinach, wash it and after it drains, salt it. Leave it with the salt for at least 1 hour and then take handfuls of the spinach and squeeze them to remove any liquids. Place them in a large bowl and add the cheese, eggs and oil.
Roll out all the sheets using corn starch.
Spread the first 4, larger sheets in the baking tray (don't forget to sprinkle the sheets with oil).
Add 1/3 of the filling.
Spread 3 more sheets over the filling.
Spread 1/3 of the filling.
Add 3 more sheets.
Add the rest of the filling and turn the sheets inwards.
Finally, cover with the 3 last, smaller filo sheets. Score the pie with a knife and pour over it a mixture that you make with 1 egg, some milk and a little bit of oil.
Bake for 1 hour at 180 degrees on the top rack, using the convection element.
