In a large bowl, combine 6 oz of strawberry Jello mix with 1 cup of boiling water. Stir until fully dissolved, about 2 minutes. Add 1 cup of cold water and refrigerate until it thickens, about 30 minutes.

Gently fold in 8 oz of Cool Whip into the thickened Jello until smooth. Be careful not to overmix.

Grease a 9-inch springform pan and pour in the Cool Whip and Jello mixture. Arrange halved fresh strawberries, then refrigerate for 30 minutes to set.

Combine 3 oz of Jello mix with 1 cup of boiling water in a separate bowl. Stir until dissolved and cool to room temperature, about 20 minutes.

Slowly pour the prepared Jello mixture over the set Cool Whip layer in the pan. Refrigerate to set completely, ideally 3-4 hours or overnight.

Remove the springform pan sides and garnish with additional sliced strawberries or whipped cream. Serve chilled.