brown sugar, baking soda, salt, and butter. mix until crumbly.
5. line a 9×13 inch baking dish with parchment paper and pour 2/3 of the oat mixture in the bottom of the pan, pressing firmly to pack it down to make the crust.
6. pour apples over the crust and spread in an even layer. pour the remaining oat mixture over the top and spread evenly.
7. bake for 30 minutes, or until golden brown. cool before cutting. 