Preheat your oven to 350°F (175°C). Grease or line an 8x8-inch baking dish with parchment paper.
Mix topping
In a large mixing bowl, combine the flour, rolled oats, coconut sugar, baking powder, and salt. Mix well.
1 ½ cups all-purpose flour, ½ cup rolled oats, ½ cup coconut sugar, ½ teaspoon baking powder, ¼ teaspoon salt
Add the melted plant-based butter and vanilla extract to the dry ingredients. Stir until the mixture resembles coarse crumbs and is well combined.
½ cup plant-based butter, 1 teaspoon vanilla extract
Set aside 1 cup of the mixture for the crumb topping. Press the remaining mixture into the bottom of the prepared baking dish to form an even crust.
Mix filling
In another bowl, mix together the diced strawberries, cornstarch, lemon juice, and maple syrup until well coated. Spread the strawberry filling evenly over the crust.
Sprinkle the reserved crumb topping evenly over the strawberry filling.
Bake
Bake in the preheated oven for 30-35 minutes, or until the top is golden brown and the strawberry filling is bubbly.
Remove from the oven and let the bars cool completely in the baking dish. Once cooled, you can refrigerate for a few hours to allow them to firm up before slicing.
Cut into squares and serve. These strawberry crumb bars can be enjoyed at room temperature or chilled.