In a large pot, heat 2 tablespoons extra-virgin olive oil over medium heat. Add garlic and green onions and cook 2-3 minutes, until tender and fragrant.
Remove from the heat and add the spinach, salt, pepper, dill, lemon and feta. Stir to combine. Set aside to cool for 10 minutes before adding in the egg. Mix in the egg to the cooled mix then set aside.
Preheat oven to 350°F (180°C). Melt the butter in a small bowl. On a large work surface, place one sheet of phyllo dough. Cover the remaining dough with a slightly damp paper towel. Brush the surface of the dough with melted butter, then place another sheet on top of the first sheet and brush that sheet with butter. Repeat this process until you have 4 layers of phyllo.
Using a pizza cutter, cut or sharp knife cut the dough into 5 equal pieces strips. (about 2.5-3 inches wide). Place 1 tablespoon of the spinach-feta filling at the bottom of each strip. Fold the corner of the dough over the filling, forming a triangle, then continue folding triangles (like you would fold a flag). Place spanakopita on the lined baking sheet and cover with another damp towel. Repeat this process until you have used all the phyllo dough and filling.
Brush the triangles with more butter on top and bake for 25-30 minutes or until golden brown. Remove from the oven and allow to cool slightly before serving. Cover and store in the fridge for up to 3 days.