Preheat oven to 350 ℉ / 176℃ and grease a 9x9 or 12x7 pan and also line with parchment paper, letting overhang to allow for easy lift-out.

Add 1 1/2 cups flour, oats, 3/4 cup brown sugar, 1 tsp salt and 1 tsp cardamon to a food processor or blender. Pulse about 5-6 times to mix dry ingredients together.

Next, add the cold cubed butter to food processor and pulse on and off until mixture is combined, and a crumbly consistency is reached. IMPORTANT: Scoop out 1 cup crumb mixture and reserve in fridge for later use.

Press the remaining crust mixture evenly into bottom of the prepared pan. Bake for 10-12 minutes, or until set and then let cool on rack while starting the filling.

In a medium bowl, combine strawberries, remaining 1/4 cup flour, 1/4 cup brown sugar, 1/2 tsp cardamon, 1/4 tsp salt and lemon zest.

Spread strawberry filling mixture evenly over cooled crust and remove reserved crust mixture from refrigerator and sprinkle in small clumps all over top of filling. (It will not be completely covering filling.) Next, evenly sprinkle almond slices over top.

Bake in center of oven, uncovered, for 30-35 minutes or until mixture is bubbly around the edges and crumble is golden brown. Let cool completely in pan on a rack, then lift out by parchment paper and cut into squares of desired size. Tip: For even easier slicing, chill in fridge before cutting into squares.