1. Dissolve yeast in a bowl filled with warm water.
2. In large bowl put 6 cups of flour. Add salt and oil, then add the yeast mixture. Knead together, adding more flour. If it's dry add up to another cup of water, to get the right consistency.
3. Put dough in a large bowl that has been lightly greased with oil - flip dough over to cover. Let rise at room temperature in a warm spot. Or preheat oven to 250º and turn off, then let dough rise in the warm oven. Let rise to double in size. About 1 hour.
4. While dough rises, clean and wash spinach, and mix filling.
5. Melt the butter and coat casserole dish (9X12). Put this in the refrigerator or freezer. This makes dough stick better.
6. When dough is doubled, divide into 3 parts.One part should be slightly larger than the other 2. Save larger section for layer two.
For layer one, roll dough on a floured surface to a size that fits the dish. Brush with melted butter.
Add half of filling.
For second layer, roll out dough again. cover and brush with melted butter. Add remainder of filling.
For final layer, roll out dough and place over filling. Brush with melted butter and Score the dough through the layers. Bake at 350º, 45 - 60 minutes.