Preheat your oven to 375°F and lightly grease a small oven-safe baking dish with a tiny drop of olive oil.
Place the thawed frozen spinach into a clean kitchen towel or nut milk bag and squeeze with significant force until all excess water is removed and the spinach is very dry.
In a medium mixing bowl, whisk together the large egg and egg whites until smooth.
Stir in the crumbled feta cheese, finely chopped scallions, minced fresh dill, sea salt, black pepper, and garlic powder.
Fold the squeezed dry spinach into the egg and cheese mixture until the greens are evenly distributed.
Lay one sheet of phyllo dough into the bottom of the prepared baking dish, lightly brushing the surface with a small amount of olive oil, and repeat this process with the remaining three sheets.
Pour the spinach and egg mixture into the center of the phyllo stack.
Gently fold the overhanging edges of the phyllo dough back over the top of the filling to create a rustic, crumpled border.
Place the dish in the oven and bake for 30 to 35 minutes until the center is firm and the phyllo pastry has turned a deep golden-brown and crispy texture.
Allow the pie to cool for 5 minutes before slicing to let the protein-rich filling set properly.