Set oven rack to the center position. Preheat to 375ºF (191ºC).
Cut a shallow “X” into the bottom of the peaches, and then blanch in boiling water for 15 seconds. Transfer peaches to a large bowl of ice water. Once cooled, peel the peaches with your fingertips. Cut peaches into ¾-inch thick slices. Alternatively, using a peeler, gently peel the peaches then cut into slices.
In a large bowl combine sliced peaches and ⅓ cup granulated sugar. Allow peaches to sit and macerate for 30 minutes.
Drain the liquid from the peaches into a bowl, and reserve ¼ cup of the juices.
In a small bowl whisk together the ¼ cup of peach juice, cornstarch, lemon juice, ¼ teaspoon cinnamon, ⅛ teaspoon nutmeg, ⅛ teaspoon ginger, and ⅛ teaspoon salt. Combine with peaches.
Lightly butter an 8 by 8-inch baking dish. Add peach filling, spreading evenly in the pan.
Crisp Topping
In a small bowl mix together the flour, rolled oats, pecans, brown sugar, ¼ teaspoon cinnamon, ¼ teaspoon salt, ¼ teaspoon ginger, and ⅛ teaspoon nutmeg.
Cut butter into small ¼-inch pieces and add to the flour mixture. Use your fingers to cut the butter into the dry ingredients, pressing together to create large pebble-shaped pieces of crisp topping, about the size of a dime.
Evenly sprinkle the crisp topping over the peaches.
Bake until the topping is golden brown and crisp, 30 to 35 minutes.
Wait for 30 to 60 minutes before serving.
Add warm peach crisp to serving bowls and top with vanilla ice cream.
Notes
Blanching peaches make for more attractive surfaces and more yield. The goal is just to separate the skin from the flesh and not to cook the peaches.
Frozen peaches can be substituted for fresh peaches. Defrost over a colander to remove excess moisture before combining with sugar.
MAKE IT GLUTEN-FREE: Use gluten-free flour (Bob's Red Mill 1:1 Baking flour recommended) and use gluten-free oats.