TO MAKE FRESH STRAWBERRY FILLING
Place mashed strawberries and water in a saucepan. Bring to a boil.
Reduce heat and simmer 3 minutes.
Strain juice from cooked strawberries and add enough water, if needed, to make 1/2 cup juice.
Discard strawberry pulp (or save it for a smoothie).
Combine sugar, cornstarch, lemon juice, and salt in saucepan. Add in strawberry juice.
Bring to a boil, stirring constantly, until clear and thick - about 4 to 5 minutes.
Remove from heat and cool slightly.
Stir in sliced strawberries.
TO MAKE BARS
Preheat the oven to 375.
Spray a 9x13 inch pan with non-stick spray.
Mix together oats, cake mix, and melted butter until it there is no more dry mix.
Press 1/2 of this mixture evenly into the bottom the prepared pan.
Spread pie filling evenly over the crust.
Sprinkle the remaining oat mixture on the top evenly.
Bake 18-23 minutes or until the top is lightly browned.
Cool before cutting into bars.