Preheat the oven to 350°F (175°C) and line an 8x8-inch baking pan with parchment paper.

In a mixing bowl, combine rolled oats, whole wheat flour, brown sugar, ground ginger, and kosher salt.

Melt the unsalted butter and mix it into the dry ingredients until clumps form, reserving ½ cup for topping later.

Press the remaining mixture firmly into the prepared pan to form the crust layer.

Bake the crust in the preheated oven for about 10 minutes until slightly golden.

Prepare the filling by mixing diced strawberries, cornstarch, lemon juice, and granulated sugar in a separate bowl.

Once the crust has cooled slightly, spread the strawberry mixture evenly over it.

Sprinkle the reserved crumble mixture evenly over the strawberry filling.

Bake the assembled bars for 30-35 minutes until the topping is golden and the filling is bubbling.

Cool completely in the pan before lifting out and slicing into squares.