1. 1. Preheat your oven to 375 F (190 C). Lightly grease an 8×8 inch baking pan or line it with parchment paper, leaving an overhang on the sides for easy removal later.

2. 2. In a medium mixing bowl, combine the rolled oats, ground cinnamon, and salt. Stir these together thoroughly to ensure the spices are evenly distributed.

3. 3. In a separate larger bowl, whisk together the unfed sourdough starter, unsweetened applesauce, maple syrup (or honey), and vanilla extract until well combined and smooth.

4. 4. Pour the wet sourdough mixture into the bowl with the dry oat mixture. Stir with a spatula until just combined. The mixture will be thick.

5. 5. Transfer about two-thirds of the oat mixture into your prepared baking pan. Using the back of a spoon or your clean hands, press it firmly and evenly into the bottom of the pan to form a compact crust.

6. 6. In a small bowl, gently toss the diced fresh strawberries with the cornstarch or arrowroot powder.

7. 7. Spread the cornstarch-coated strawberries evenly over the pressed oat base in the pan. Then, crumble the remaining one-third of the oat mixture over the top of the strawberries.

8. 8. Place the pan in the preheated oven and bake for 25-30 minutes, or until the top is lightly golden brown and the strawberry filling is bubbly. Let the bars cool completely in the pan on a wire rack before slicing.