Preheat the Oven: Set the oven to 350°F and line an 8-inch square pan with parchment paper, leaving some overhang for easy removal.
Prepare the Base: In a bowl, combine almond flour, oats, cinnamon, melted butter, maple syrup, and vanilla extract. Stir until a crumbly mixture forms. Reserve a quarter of this mixture for the topping. Press the rest firmly into the pan to form an even layer. Bake for 13-15 minutes, until slightly golden.
Make the Filling: In a small saucepan over medium heat, cook the raspberries, maple syrup, and lemon juice for about 5-7 minutes, stirring and mashing the fruit until it forms a thick puree. Remove from heat, then mix in chia seeds and tapioca flour.
Assemble the Bars: Once the base has cooled slightly, spread the raspberry filling evenly over it.
Add the Topping: To the reserved base mixture, stir in chopped pecans. Sprinkle this crumble over the raspberry layer and gently press it in.
Bake the Bars: Return the pan to the oven and bake for 25-30 minutes, or until the topping is golden.
Cool and Slice: Let the bars cool completely in the pan before slicing. This prevents them from falling apart.