Preheat your oven to 350°F (175°C).
In a large mixing bowl, gently toss the sliced peaches with sugar, cornstarch, cinnamon, and ginger until well coated. The fruit should look glossy and slightly thickened.
6 cups ripe peaches, sliced
Transfer the peach mixture into a baking dish, spreading it out evenly to form a nice, level layer.
In a separate bowl, combine oats, flour, brown sugar, and salt. Mix them together before adding the cold butter pieces.
6 cups ripe peaches, sliced
Use a pastry cutter or forks to cut the cold butter into the dry ingredients until the mixture resembles coarse crumbs with some pea-sized bits.
6 cups ripe peaches, sliced
Sprinkle the crumble topping evenly over the peaches, covering the entire surface with a generous layer of crumbs.
Bake in the preheated oven for about 40 minutes, or until the topping is golden brown and the filling is bubbling at the edges.
Remove the peach crisp from the oven and let it rest for a few minutes to set slightly. It will be hot and bubbling.
Serve the warm peach crisp with a scoop of vanilla ice cream or a dollop of whipped cream, if desired.
