Preheat oven to 350°F. Line a square (8x8) baking dish with parchment paper.
Add apples, cinnamon, nutmeg, water and arrowroot powder into a saucepan. Cook over medium-high heat for about 15-20 minutes, stirring often and watching to make sure the mixture doesn’t burn. You’ll know it’s done when the mixture has thickened and the apples are soft, but still hold their shape. Remove from heat, stir in vanilla and set aside.
Add 1 cup of oats to your food processor and process until oats turn into a fine oat flour.
Add remaining cup of oats, coconut sugar, coconut oil and sea salt into the food processor and pulse until everything is combined and the size of coarse crumbs. Don't over process the mixture, you want to be able to visibly see some of the oat flakes.
Measure out ⅔ cup of the oatmeal crumble mixture for the topping into small bowl and stir in the chopped pecans.
Use remaining oatmeal crumble mixture to create crust. Evenly press into the parchment lined baking dish using your hands.
Pour apple filling on top and sprinkle the oatmeal + pecan crumble on top.
Bake for 35-40 minutes until the bars are golden brown on top. Remove from oven and place on a wire rack to cool completely. Be patient, if you don’t let them cool before removing them from the pan they will fall apart. I recommend putting them in the fridge or freezer to chill, about an hour or so.
Once cool, cut into 9-12 bars and enjoy right away or chill longer in the fridge before serving. I personally like the bars chilled because they hold together better if you're eating them as a snack. If you're serving them for dessert, I recommend placing a portion into a bowl, warming in the microwave and topping with ice cream.
Leftover bars will keep for 4-5 days in the fridge in an airtight container. You can also freeze them for longer storage.