Refer to page X in the Cake Class chapter for a step-by-step picture tutorial for stacking cakes like this. The cakes may be different flavors, but the assembly steps are similar.
Put a piece of parchment paper on the counter. Invert the cake onto the parchment and peel off the parchment from the bottom of the cake.
Use a 6-inch cake ring to cut out 2 circles from the cake and two half circles. The two full circles will be your top 2 cake layers. The two half cake layers and remaining cake scraps will come together to make the bottom layer of the cake.
For the first layer, clean the cake ring and place it in the center of a sheet pan lined with clean parchment. Line the cake ring with one strip of acetate.
Place the two half circles against the edge of the acetate and fill the gap with the extra cake scraps.
Use the back of a spoon to spread one-third of the banana cream pudding in an even layer over the cake.
Spread sliced bananas evenly over the pudding (if using).
Sprinkle 1/2 cup of the graham cracker crumbs on top of the bananas, followed by a heavy drizzle of the salted caramel.
Carefully spread about 1/2 cup of the whipping cream on top.
Gently tuck in another strip of the acetate paper between the cake ring and the top quarter inch of the first acetate strip, high enough to support the height of the finished cake.
Set a cake round on top of the whipped cream and repeat steps 6-9.
Set the final cake layer onto the whipped cream and cover the top of the cake with the remaining banana cream pudding, graham cracker crumbs, caramel, and whipped cream.
Transfer the sheet pan to the freezer and freeze for at least 12 hours. About 4-5 hours before you're ready to serve, remove the cake from the freezer and transfer to the refrigerator to finish thawing.