Preheat oven to 375°F. Combine sugar and 1 tsp. cinnamon in a small bowl; set aside. In a 15x10x1-inch baking sheet, stir together flour and salt. Form a well in the center and pour in oil and milk. Stir together with a fork until liquid is fully incorporated and the mixture is moist and crumbly; set aside 1 cup of dough for topping. If dough is too dry and crumbly, add water 1 tsp. at a time to reach a consistency that is easy to press in Step 2.

Press dough evenly along the bottom and up the sides of the pan. Flute the edges by pressing dough with knuckles against side of pan.

Press reserved 1 cup of dough to 1/4-inch thickness between two sheets of waxed or parchment paper and cut out shapes with a cookie cutter (about 20 shapes with a 2-inch cutter, or 15 shapes with a 3-inch cutter). Refrigerate dough shapes on paper while preparing pie filling.

Combine cornstarch and remaining 1 tsp. cinnamon in a large bowl. Drain peaches, reserving 2 cups syrup. Add reserved syrup to the cornstarch mixture and stir with a whisk to avoid lumps. Stir in peaches and carefully pour onto crust in baking pan. Distribute peaches evenly over crust. Top peaches with chilled dough shapes. Sprinkle shapes lightly with reserved cinnamon-sugar mixture.

Place pan on a middle rack of oven and bake 55 minutes or until juices are bubbling and crust edges are lightly browned. Cool on a rack at least 15 minutes before serving. Serve with frozen yogurt or ice cream, if desired.