Preheat oven to 350 F. Thaw phyllo dough according to package instructions, likely in the fridge overnight or at room temp for 3 hours.
Chop washed spinach and place in a large bowl. Add 1 tbsp salt and rub together using your hands. Set aside.
Slice green onions, chop fresh parsley, fresh dill, and set aside. In a separate small bowl, lightly beat two eggs.
Using your hands, squeeze the water out of the spinach and carefully transfer to a separate large mixing bowl.
Add 1/4 cup olive oil to the bowl with the drained spinach. Add the sliced green onions, chopped parsley, chopped dill, crumbled feta, beaten eggs, and black pepper. Combine all ingredients using your hands.
In a microwave safe bowl, melt butter for 30 seconds and mix in olive oil. Brush the bottom of your baking dish with the butter/oil mixture.
Remove one sheet of thawed phyllo dough and place on the bottom of the baking dish. Brush with the butter/oil mixture. Repeat with 7 more sheets of phyllo, arranging so the dish is covered (the sheets should overlap and spill over the sides of baking dish).
Spread the spinach and feta filling into the baking dish in an even layer. Fold the overhanging phyllo dough back over the filling, brush with butter/oil mixture.
Layer top with 2 flat sheets of phyllo dough, brushing each with the butter/oil mixture. Using 6 more sheets of phyllo, keep a flat top by laying each sheet down in flat layers and sealing in the sides OR make a fluffy top by lightly crinkling the phyllo sheets before placing on top.
Cut your spanakopita into even squares prior to baking, this will make cutting and serving it easier.
Place baking dish in the preheated oven for 45 minutes. Slice into even pieces again and serve warm.