Gently fold in half of the whipped topping (about 4 oz) into the pudding mixture using a spatula, just until no streaks remain. This lightens the filling and helps it set into fluffy layers.
Lay a single layer of graham crackers on the bottom of the 9×13-inch glass baking dish, breaking pieces as needed to fully cover the bottom. Neat rows make those pretty stacked cracker edges when you slice it.
Spread about one-third of the lemon pudding mixture evenly over the graham cracker layer, smoothing it all the way to the edges so the crackers are fully covered.
Add another single layer of graham crackers over the pudding, again covering the entire surface. Repeat with another one-third of the pudding mixture, smoothing it out.
Finish with a third and final layer of graham crackers, then spread the remaining pudding mixture over the top, making sure no crackers are exposed.
Spoon the remaining whipped topping over the final pudding layer and gently spread it into a fluffy, even layer. This becomes the smooth, creamy top you’ll see through the glass dish.
Cover the dish tightly with plastic wrap or a lid and refrigerate for at least 4 hours, or overnight if you have time. This chill time is when the “no-oven miracle” happens—the graham crackers soften into a cake-like texture and the layers set.
When ready to serve, remove from the fridge and use a sharp knife to cut into neat squares, wiping the knife between cuts for clean layers. Serve directly from the glass dish, showing off those creamy lemon and graham cracker stripes.
Store any leftovers covered in the refrigerator for up to 3 days. The layers will continue to soften, which honestly makes it even better by day two.
