Preheat the oven to 375 degrees F. Start by making the crumble topping. In a large bowl, combine the dry ingredients. Combine flour, brown sugar, cinnamon, ginger, nutmeg, and kosher salt. Whisk together, then add the cubed butter and pinch the butter into the mixture until crumbles begin to form and you no longer see big chunks of butter. Place into the refrigerator.
Slice peaches and add them to larger mixing bowl and toss them with brown sugar, cinnamon, melted butter, vanilla extract, and salt.
Place peach slices in a 9 inch pie pan or 10-inch cast iron skillet.
Remove crumble topping from the refrigerator and sprinkle on top of the peaches in an even layer.
Bake in the preheated oven for 45-55 minutes, until the peaches are bubbly and the crumble topping is golden brown.