Rhubarb Hazelnut Oatmeal Squares

Name: Rhubarb Hazelnut Oatmeal Squares
Ingredients: For Rhubarb; 3 1/2 cups Fresh rhubarb, cut into 1-inch chunks; 2/3 cup sugar; 2 tablespoons cornstarch; 1/4 cup orange juice; 1/4 teaspoon nutmeg; 1 teaspoon vanilla; For the Hazelnut Oatmeal Crumble; 1 1/2 cups quick oatmeal; 1 1/2 cups flour; 1/2 teaspoon baking soda; 2/3 cup dark brown sugar; 1/2 cup hazelnuts, finely chopped; 1 1/2 sticks unsalted butter, room temperature