Thick white foam
2 pieces 1 3/4" x 1 3/4" light brown foam
1 1/4" x 2 1/2" dark brown foam
See the Miscellaneous section for more instructions, hints and tips.
You might be interested in learning more about the history of the marshmallow.
S'mores are made by first roasting a marshmallow. Stick a marshmallow on the end of a long stick or wire and rotate it over hot coals until it turns light brown. Place part of a chocolate bar on a graham cracker, place the marshmallow on top of the chocolate and cover it with a second graham cracker. Then pull out the stick or wire. Be very careful because the wire will get very hot. The wire or stick can easily poke someone else because your attention is focused on the S'more you just made and are getting ready to eat.
For the marshmallow, you can use thick craft foam or shape a piece of Styrofoam with a knife and sandpaper.
If you are ambitious, you could make a marshmallow (white pony bead on a 1/8" dowel rod or other stick) being roasted over a campfire.