Preheat and bake the frozen pie crust according to the package directions. Let it cool completely on a wire rack.

In a large saucepan, combine the sugar and 1 1/2 cups water. Warm over medium heat until the sugar dissolves and the liquid is warm but not boiling.

In a small bowl, stir the cornstarch into a few tablespoons of the warm water to make a smooth slurry with no lumps.

Whisk the cornstarch slurry slowly into the warm sugar water. Keep whisking to prevent lumps.

Continue stirring for 4 to 5 minutes as the mixture thickens and becomes slightly clear. It should coat the back of a spoon.

Remove the pan from heat. Whisk in the strawberry agar-agar until it dissolves completely.

Let the glaze cool to room temperature so it won’t cook the berries.

Place the sliced strawberries in a bowl. Pour the cooled glaze over the berries and toss gently to coat each slice.

Spoon the glazed strawberries into the cooled pie crust and spread into an even layer.

Refrigerate the pie for 2 to 3 hours, or until the filling is set.

Serve chilled, optionally adding a dollop of whipped cream.