Preheat the oven to 200°C/fan 180°C/gas mark 6. Brush a round, 20cm loose-based cake tin with a little oil. Layer 3 sheets of filo in the base and up the sides of the tin, brushing each sheet with more oil.
Squeeze any excess water out of the defrosted spinach. Put the spinach in a large bowl and stir in the carrot, parsley, oregano, pine nuts and feta. Add the eggs and season, then mix well until combined. Spoon the spinach mixture into the tin and fold the overhanging pastry over the top of the mixture.
Top with the remaining 3 sheets of filo, scrunching a little to fit the tin and brushing the top of each with a little oil. Bake for 35-40 minutes, until golden and crisp, then cut into wedges to serve.