If using frozen phyllo dough, ensure it's fully thawed. Preheat the oven to 350°F (175°C).
Trim the filo sheets to fit a tray size of 9"x9" (22 cm x 22 cm). Cover the sheets with a damp cloth to prevent drying.
Mix the melted clarified butter and vegetable oil in a bowl.
Place the first sheet of phyllo dough in the dish and brush it with the melted butter mixture. You don’t need to brush each layer thoroughly.
Repeat this process, layering and buttering each sheet, until you've used half of the phyllo sheets.
Evenly distribute the chopped nuts over the layered phyllo sheets and then press them down lightly.
Place the remaining phyllo sheets over the nut layer, brushing each with melted butter.
Once all sheets are layered, brush the top with butter and cut the baklava into desired shapes and sizes, such as squares or diamonds.