Preheat the oven to 350deg F. Grease a 9x9-inch square baking dish. To make the crust, combine the flour, rolled oats, sugar, cinnamon, and salt in the bowl of an electric mixer fitted with a paddle attachment. Mix together, then add in the cubes of cold butter. Beat on medium speed until the mixture is crumbly and the consistency of coarse sand. (Alternatively: cut butter into ingredients by hand in a large mixing bowl.) Set aside 1 1/2 cups of the crust mixture. Press the rest into the bottom of the prepared pan, creating an even layer. Bake the crust for 15 minutes, until golden. To make the filling, place the diced peaches in a large bowl. Add in the lemon juice, flour, sugar, salt, cinnamon, and ginger and stir to mix. Spread the peach mixture evenly over the baked crust. Crumble the remaining crust dough over the peaches, covering as much of the surface as possible. Bake the pie bars for 45 minutes, or until the top is slightly browned and the filling is visibly bubbling. Cool completely in the pan. Whisk together the confectioners sugar and heavy cream to make the glaze. For a thinner glaze, add more cream; for a thicker glaze, add more sugar. Drizzle over the top and allow the glaze to solidify before cutting into squares. Notes: Use fully ripe peaches for the best flavor. After baking, allow the bars to cool completely before slicing. Leftover peach pie bars are best consumed the day they are baked. Leftovers can be stored at room temperature or refrigerated for 2-3 days, or frozen for 3 months. Individual bars should be wrapped in aluminum foil and stored in an airtight freezer bag. Thaw to room temperature