Preheat oven to 350° F. Line a square (8x8) baking dish with parchment paper.
Add blueberries, lemon zest, water and arrowroot powder into a saucepan. Bring to a boil over medium-high heat. Reduce heat to a simmer and stir constantly for about 3-5 minutes or until mixture has thickened and some of the blueberries have started to pop. Remove from heat 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 2/3 cup of the oatmeal crumble mixture for the topping into small bowl and stir in the hemp hearts.
Use remaining oatmeal crumble mixture to create crust. Evenly press into the parchment lined baking dish using your hands.
Pour blueberry filling on top and sprinkle the oatmeal + hemp crumble on top.
Bake for 35-40 minutes until the bars are golden brown on top and the blueberry filling is bubbling and sticking to the edges of the pan. 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.
Once cool, cut into 9-12 bars and enjoy right away or chill in the fridge before serving. I personally like the bars chilled, after they've been in the fridge for a bit.
Leftover bars will last 3-4 days in the fridge.