The topping, which contributes about 10 calories per bar, is optional, though I think the crystallized ginger adds a lot of zing to these tasty bites. They improve with age, so consider making them a day ahead of serving.
Preheat oven to 375 F. Line the bottom of a 9×13-inch nonstick baking pan with parchment paper.
Crust: Place 1/2 cup of the oats in a blender and crush them to a fine powder. Pour the oat flour into a medium mixing bowl and add the remaining oatmeal and the other dry crust ingredients. Add the apple sauce and water and stir until well-moistened. If necessary, add additional water a teaspoon at a time until all flour is moist. Pour it into the prepared pan and press it into the pan until the bottom is evenly covered.
Filling: Place all the filling ingredients into a blender or food processor. Process until all ingredients are thoroughly combined. Pour filling on top of crust and smooth with a spatula.
Topping and Baking: Mix the topping ingredients together and sprinkle on top of the filling. Bake for 40-45 minutes, until pumpkin is set in the middle. Remove from oven and run a non-metal knife or spatula around the edges. Cool for at least 15 minutes before cutting into 48 squares.
*Gluten-free results depend on using certified gluten-free oats and other ingredients.