Begin by preheating the oven to a temperature of 350°F (175°C). Following this, meticulously grease a baking dish, ideally measuring 9x13 inches, using a nonstick cooking spray.

In a mixing bowl of appropriate size, combine the graham cracker crumbs and melted butter. Once combined thoroughly, transfer this mixture to the aforementioned baking dish, ensuring to press it evenly at the bottom to form the foundational crust.

Proceed by uniformly pouring the sweetened condensed milk over the previously prepared crust. Upon completion, layer the chocolate morsels over the milk, followed by an even spread of the flaked coconut. Conclude this step by evenly distributing the chopped walnuts or pecans over the previous layers. To ensure a consolidated layering, press down the contents with moderate force using a fork.

Place the baking dish in the preheated oven and allow it to bake until it achieves a light brown hue, typically within a 25-30 minute window. Post baking, utilize a knife with a buttered edge to carefully run along the dish's perimeter, ensuring the contents are not adhering to the sides. Subsequently, position the dish on a wire rack, permitting it to cool.

After ensuring the contents have cooled to a satisfactory degree, use a sharp knife to partition the baked mixture into individual squares. These squares are now ready to be served.