Preheat the oven to 400°F.
Add the flour, brown sugar, cinnamon, and butter to the bowl you used for the peaches and mix the ingredients together until it forms a wet, clumpy mixture.
Add the oats to the mixture and combine using your hands or a large spoon.
Butter an 8x8 baking pan, and set aside until needed.
Add the peaches, granulated sugar, flour, cornstarch, and salt to a large bowl and mix to combine.
Add the peach mixture to the prepared pan.
Sprinkle the topping over the prepared peaches in an even layer. Don't pack the topping down, leave it loose and crumbly.
Place the baking dish on the center rack of the preheated oven and bake for 20 - 25 minutes, until the oats start to lightly brown.Remove the peach crisp from the oven and let it sit for 10-15 before serving.
Serve warm, with vanilla ice cream.
