Position an oven rack in the center of the oven and preheat to 350 degrees F.
In a food processor, grind the nuts until they are coarsely, but not fully ground. Mix the nuts with the ground cinnamon. Using a soft pastry brush, lightly butter a 9 1/2 by 7 1/2-inches ovenproof dish. Gently unfold the filo pastry, covering it immediately with a clean, damp tea or kitchen towel, to stop it from drying out, and cracking.
Start layering the sheets of filo pastry into the dish, brushing each sheet with the melted butter before placing the next layer on top. After six layers, spread a third of the nuts evenly over the filo.
Alternate the 6 sheets of filo-butter layer and a third of the nut mixture twice more, and then top with 6 more layers of filo pastry. Butter the top of the last layer, and trim off any overlapping pastry with a sharp knife to create a neat edge. Cut into small diamonds, about 1 1/2 to 2-inch squares, making sure the knife goes all the way through the bottom layer.
Bake until golden brown and crisp, about 40 to 45 minutes, reducing the temperature to 325 degrees F, during cooking if the baklava looks as though it is browning too quickly.
To make the syrup: In a saucepan set over a medium heat, combine the water, sugar, honey, cinnamon, orange zest, cloves and orange-flower water, if using. Simmer for about 15 minutes, allowing the liquid to reduce by about 1/3. The liquid should thicken slightly. Stir occasionally, and then leave to cool while the baklava is baking.
Remove the baklava from the oven, and spoon half of the cooked syrup all over the top. Leave for 5 minutes, and then pour the remaining syrup over top. Let the baklava cool completely before removing the individual pieces from the dish with a palette knife.
Recipe courtesy of Rachel Allen