Put oven rack in middle position and preheat oven to 350°F.
Whisk together almonds, walnuts, sugar, cinnamon, nutmeg, cloves, and salt until combined well.
Generously brush a 13- by 9- by 2-inch glass baking dish with melted butter. Half phyllo sheets crosswise and stack sheets. Keep stack covered with 2 overlapping sheets of plastic wrap and then a dampened clean kitchen towel. Lay 2 sheets of phyllo in bottom of baking dish and brush top sheet generously with butter. Continue to layer 2 sheets at a time, staggering sheets in each double layer slightly to cover bottom of dish, then brushing every second sheet generously with butter, until you have used 10 sheets of phyllo total. After brushing top layer of phyllo with butter, spread a rounded 1 1/2 cups of nut mixture over it. Drizzle with 2 tablespoons butter.
Repeat layering 3 more times. Top with 10 more sheets of phyllo. (You will use 50 sheets of phyllo total.) Butter top and let baklava stand at room temperature to harden slightly (to facilitate cutting), 10 to 15 minutes.