Preheat the oven to 400°F. Lightly grease a 9-by-13-inch baking pan with nonstick spray and line with parchment paper. Let a little bit of extra paper hang off the edges.Preheat the oven to 400°F. Lightly grease a 9-by-13-inch baking pan with nonstick spray and line with parchment paper. Let a little bit of extra paper hang off the edges.

Pulse the graham crackers in a food processor until they are finely ground. Transfer the crumbs to a medium bowl. You can also task the kids with crushing the graham crackers into crumbs in a secure plastic bag!

Add the sugar, salt, and butter to the crumbs and stir to combine until evenly coated. Pour the crumb mixture press evenly into the pan

Bake the crust for 8 to 10 minutes, or until the edges are lightly golden. Let the crust cool.

Arrange the chocolate bars evenly on top of the slightly cooled crust, leaving a bit of crust uncovered around the edges.

Arrange the marshmallows on top of the chocolate. Leave some space between them (they will expand).

Bake until the chocolate is soft and starting to melt, and the marshmallows are evenly toasted golden brown on top, around 10 to 12 minutes.