To peel peaches: Bring a pot of water to a boil. Use a sharp paring knife to make a small "x" through the skin at the base of each peach. Prepare a large bowl of ice water. Boil them for 40 seconds. If peaches are slightly under-ripe, allow them to remain in the hot water a little longer—up to a full minute—to loosen the peel, it will also improve their flavor. Use a slotted spoon to transfer the boiled peaches to the bowl of ice water. Leave them to cool, about 1 minute. Drain the peaches and pat them dry. Slip the skin off the peaches using your fingers or a paring knife.
Preheat oven to 425° degrees. In a small bowl, combine all the dry ingredients for the peach filling. Stir to combine and set aside. In a large bowl, combine the sliced peaches and the lemon juice and then add the dry ingredients. Stir well to coat evenly and pour into a large 9x13 baking dish.
Bake the peach mixture in the preheated oven for 10 minutes. While the peaches are baking, combine the dry topping ingredients and whisk to combine. Blend in the chilled butter, using a pastry blender or your fingertips. Stir in the boiling water, just until combined.
Remove the peaches from the oven and mix juice over peaches in pan. Drop the topping over peaches in spoonfuls. Sprinkle the cobbler topping with the cinnamon sugar mixture. Bake until the crust is golden and a toothpick inserted into the crust comes out clean, about 30 minutes. Serve warm or at room temperature.