Place 4 halves on a single layer in the air fryer basket.
With a knife or scissors to cut the marshmallows in half then press them sticky side down onto the graham cracker squares in the basket. This will ensure the marshmallows stay in place don't get blown around as they cook in the air fryer.
Air fry at 350℉ for 3 to 4 minutes.
Open the air fryer and then top each square with broken pieces broken of the Hershey’s chocolate bar
Bring the Graham crackers with toppings out of the air fryer and cover with the other halves of Graham crackers. The heat from the marshmallows will melt the chocolate. See note 3 if you are having trouble with the chocolate melting.
Notes
Do not skip cutting the marshmallows. The cut edge is sticky and helps the marshmallows stick to the graham crackers so that it doesn't get blown away as it cooks.
No need to preheat the air fryer however the batches after the first will take less time since the air fryer got preheated while it cooked that first batch.
After the first 3 to 4 minutes my marshmallows are hot enough to melt the chocolate. If you find that your chocolate isn't melting like you want it to, just push the basket back in. The residual heat should fix that or you can cook for an additional minute.
Since air fryers cook differently and marshmallows can burn quickly, keep an eye on your s’mores as they cook.