Arrange 12 of the ice cream sandwiches in the bottom of a 9x13 pan. Spread 1/2 of the whipped topping on top of the sandwiches. Spoon 1/2 of the hot fudge on top of the whipped topping. Place remaining 12 ice cream sandwiches on top of the fudge, spread on the rest of the whipped topping, then finish the layers with the remaining hot fudge. Cover and place in the freezer for 2 hours to set. Let soften at room temperature briefly before cutting into squares.