The recipe for these spinach and feta appetizer triangles came from a Greek family friend. They may be frozen prior to baking.
If you're making these ahead of time, proceed up to Step 5. Freeze triangles on a baking sheet until firm, then transfer to a freezer bag. To bake, arrange pastries on a lightly greased or parchment-lined baking sheet. Bake until phyllo is golden brown and filling is hot; start checking for doneness after 1 hour.