In a large mixing bowl, add the strawberries, sugar, lemon juice, cornstarch & toss to combine. (If the sugar hasn’t dissolved fully don't worry because it liquifies while baking)
Evenly distribute the mixture over the crumble crust.
Add the reserved 250g crumble evenly over the top & you can use the spatula again to make sure it is evenly spread throughout the pan.
Place in the oven & bake for 50 minutes. Crumble should appear set and very pale golden and the strawberry filling mixture will be bubbling along the edges.
Bars may take longer than 50 to 55 minutes if the strawberries are very juicy. Watch your bars, not the clock, when evaluating doneness.
Place pan on a rack or wooden board & allow to cool for at least 1 hour before slicing and serving. If you try to slice bars before they’ve cooled completely, they’ll be extremely messy and could fall apart.