In a large mixing bowl, combine the softened butter and brown sugar. Beat until smooth and creamy. Gradually add the flour, blending it into the butter mixture using a pastry blender or fork until a crumbly texture forms. Incorporate the sliced almonds, ensuring even distribution.

Firmly press the crust mixture into a greased 9x13-inch pan, spreading it evenly. Bake in a preheated oven at 350°F (175°C) for 10 minutes. Remove and allow to cool completely before proceeding.

In a medium bowl, dissolve the Lemon Jello powder in 2 cups of hot water, stirring until fully dissolved. Set aside and allow it to cool completely. This step is crucial to prevent melting the cream cheese during the next stage.

In a separate large bowl, whip the softened cream cheese and granulated sugar until smooth and creamy. Ensure there are no lumps for a velvety filling texture.

Using a chilled bowl and whisk or an electric mixer, whip the whipping cream until it reaches stiff peaks. This process creates the light, airy texture essential for the filling.

Once the Lemon Jello mixture has cooled, gradually blend it into the cream cheese mixture. Whisk until the color is uniform and the mixture is smooth. Gently fold the whipped cream into the combined mixture using a spatula, taking care not to deflate the whipped cream.

Pour the filling over the cooled crust, spreading it evenly with a spatula. Smooth the surface for a uniform appearance.

Place the cheesecake in the refrigerator and allow it to chill for at least 4 hours, or preferably overnight, until the filling is firm and fully set.

Slice into squares or desired portions, garnish as preferred, and serve chilled.