How to cut a cake that was baked in a pie pan?
Invert the bottom layer, top down, on a plate. Add the ice cream, but do not spread it to the outside edge of the cake. Top with the second cake layer, pressing gently. Then, using a sharp knife, slice vertically completely around the edge, removing the sloped edges of the cake. Surround the outside edge with a wrap of parchment paper or foil. Chill. After the cake is firm, you can slice horizontally to level the mound at the top of the cake, if you wish, before removing the paper/foil cuff.