Preheat the oven to 350°F (180°C).
Butter a large sheet pan really well. Mine is about 14 X 12 inches (37 x 31 cm). Set aside.
Start detangling the shredded phyllo dough. Pull apart all the strands without ripping or tearing the dough, so that there aren't any knots left. Work as quickly as you can as the dough can dry out very quickly. You should end up with a big fluffy pile of dough (see picture 5 in the post).
Mix the ground cinnamon with the nuts in a small bowl. Set aside.
Evenly spread half of the detangled phyllo dough on your prepared pan. Then sprinkle with the nut mixture.
Pour half of the melted butter on top.
Spread the remaining phyllo dough and add the remaining melted butter. Use your hands to toss everything together so that the shredded dough is coated with the melted butter as much as possible. Make sure there aren’t any empty spaces. If there are, just use your fingers to push the shredded dough to fill them in. Don’t press down on the dough.
Bake the base for about 30-35 minutes, until it has a nice golden brown color (see picture 10 in the post).
When the base is done, take it out of the oven and immediately pour ALL of the cooled syrup all over. It will sizzle! This is completely normal! It will look like it’s too much syrup, but trust me, it isn’t!
Carefully tilt the pan left and right so that the syrup goes everywhere. Wear gloves if your pan is still hot! Set the base aside.