In a large mixing bowl, dissolve the instant yeast in the warm water. Add the granulated sugar and stir gently. Allow to sit for 5-10 minutes until frothy.
Add 2 cups of flour, salt, and olive oil to the yeast mixture. Mix until a dough forms, then gradually add the remaining flour until not sticky.
Knead the dough on a floured surface for 5-7 minutes until smooth and elastic. Shape into a ball, place in a greased bowl, cover, and let rise for 1 hour.
While the dough rises, sauté the spinach in a skillet until wilted. Add green onions if using, and season with salt and pepper. Let cool.
After the dough has risen, punch it down and divide into 10-12 pieces. Roll each into a ball and then into a 6-inch circle.
Place 1-2 tablespoons of spinach filling in the center, fold over to create a half-moon, and pinch edges to seal.
Preheat oven to 375°F (190°C). Line a baking sheet with parchment paper. Place pies on the sheet and brush tops with olive oil or water.
Bake for 25-30 minutes until golden brown. Let cool slightly on a wire rack before serving.
Notes
For extra flavor, add spices like cumin or nutmeg. You can freeze the pies before baking for later use.