Preheat the oven to 350°F and prepare the baking dish with non-stick spray and/or parchment paper. Combine all of the ingredients for the cherry filling in a bowl and stir together gently to combine. Place in the refrigerator until ready to build the bars.
In another bowl place the flour, oats, brown sugar, baking soda, nutmeg, cinnamon, and salt. Stir to combine everything. Add the melted butter a little at a time to combine completely with the flour mixture.
Take ⅓ of the crumble mixture and place it in the bottom of the prepared pan. Evenly spread out along the bottom and gently press with fingers to create an even crust. Bake bottom crust for 12 minutes, remove and cool for at least 10 minutes.
Once the crust has cooled, take the cherry mixture out of the fridge and evenly distribute it on the baked bottom. Sprinkle the reserved crumble mixture over the top of the cherries and gently press down to pack in the crumble top.
Bake again for 25 minutes. The topping will brown slightly, but not too much. Remove from oven and cool in the pan. The bars will be soft when warm and more firm when chilled. Enjoy!