Preheat your oven to 375°F (190°C). In a large mixing bowl, toss the sliced strawberries with sugar and lemon juice until well coated. Transfer the sweetened strawberries to a baking dish, spreading them out evenly.
In a separate bowl, combine flour, rolled oats, brown sugar, and cinnamon. Mix briefly to evenly distribute the dry ingredients.
Add the chilled, cubed butter to the dry mixture. Using a pastry cutter or fork, cut the butter into the mixture until it resembles coarse crumbs with some pea-sized pieces.
Sprinkle the crumbly topping evenly over the strawberry filling, covering all the fruit to create a layered look.
Place the baking dish in the oven and bake for about 35 minutes, or until the topping is golden brown and the filling is bubbling around the edges.
Remove the crumble from the oven and let it cool slightly; the topping will become crispier as it cools. Serve warm with a scoop of ice cream or a dollop of fresh cream if desired.