In a large bowl, combine the peaches, sugar, and cinnamon. Add the cornstarch to a small bowl and whisk in the lemon juice so no lumps remain. Pour the cornstarch mixture over the peaches and toss. Let the peaches sit for 15 minutes while you roll out the pie dough and make the streusel topping.
To make the topping:
Mix the flour, brown sugar, cinnamon, allspice, and salt in a large bowl. Blend the butter into the mixture with your fingers until it forms pea-size lumps and looks crumbly. Stir in the almonds.
Roll out the dough an extra inch on a lightly-floured surface. Place the dough in the bottom of a 9-inch pie pan. Crimp edges as desired.
Pour the pie filling into the pie shell and sprinkle the streusel topping over the pie. Dot the top with sliced butter. Bake for 45 to 50 minutes. Remove from the oven and let cool before serving.