In a large bowl, mix together cereal, toasted almonds, toasted coconut, brown sugar and butter. Press half of mixture into the bottom of a 13 x 9 x 2-inch baking dish and chill slightly. Spoon softened ice cream over chilled crust and press evenly, using waxed paper and your hands. Top with remaining crumb mixture. Cover and freeze for at least 4 hours or overnight.
To serve, cut into 8 equal squares. Cut each square diagonally into triangles. Drizzle with caramel sauce, if desired.