Preheat the oven to 375°F. Lightly grease a 12" cast-iron skillet with vegan butter.
Start by making the crisp: In a medium bowl, combine the flour, oats, brown sugar, baking powder, cinnamon and salt. Add the vegan butter and combine with the dry ingredients using your fingers or a fork until everything is moist and clumps together. Set it aside in the fridge while you prepare the rest of the recipe.
In a medium-large bowl, whisk together the lemon juice, brown sugar, 2 tablespoons of flour, vanilla, cinnamon, salt and water. Peel and slice the peaches and transfer them to the same bowl. Stir it all together.
Spread the peaches in the prepared cast-iron skillet. Top with the crisp topping.
Bake for 35-40 minutes at 375°F. Remove from the oven and let it cool slightly. Serve with your favorite ice cream.