Add flour, oats, white sugar, brown sugar, salt and baking soda to a large mixing bowl and stir to combine.
Add melted coconut oil and vanilla extract to the mixture and stir until well combined.
Once the mixture is well combined, divide in half. Press one half into the bottom of an 8x8 square baking pan. Bake for 15 minutes.
While that's baking, add the sugar and arrowroot powder to a mixing bowl and mix well. Add lemon juice and water and mix well.
Lay the apples out in the pan and then top with the pomegranate seeds.
Pour the liquid mixture over the apples and pomegranate seeds, then return the pan to the oven for about 20 minutes.
Remove from the oven and sprinkle the remaining crumb mixture over the top of the pomegranate apple filling. You'll want to crumble it in your hands and sprinkle it gently - don't pack it in too tight.
Return the pan to the oven for another 30-35 minutes, or the top layer is golden brown. Remove from oven. If you're serving warm, you can serve right away as a crumble in a bowl topped with vanilla bean ice cream.
If you want to serve cold, allow the Pomegranate Apple Crumble Bars to cool for an hour before transferring to the fridge. You'll want to let it cool for about 3 hours or overnight. Then remove from the fridge and cut into bars or squares. They're great served with ice cream cold too!