Into a saucepan, start by adding the strawberries, 3 to 4 tablespoons of sugar and the juice of ½ lemon, mix very well, bring saucepan to a boil over low heat and stir. Let it cook for 10 minutes.
Transfer the strawberry mixture to a blender, blend very well until combined, transfer it to a bowl and let it chill in the fridge for a bit.
Fill the edges and the bottom of a 21x11cm rectangular mold with thin strawberry round slices and set aside.
Into a bowl, add the whipped cream mix and 1 to 2 tablespoons of sugar. With a mixer, whip it very well into whipped cream.
Gradually pour the strawberry mixture into the whipped cream and gently mix until combined.
Transfer the strawberry cream to the mold filled with strawberry slices and evenly spread it.
Let it chill in the freezer for at least 4 hours.
Finally, put this mold into a baking dish filled with hot water for 30 seconds to help unmold.
Serve.