This is called a Swedish flame. Make your cuts like you're cutting cake, leave about 6 inches at the base, throw about a cap full of fuel oil in it. It burns up to two to three hours Can use olive oil instead of fuel oil :-) Any oil will burn!
Instead of using that plain marshmallow for some S'mores. why not try stuffing candy into the marshmallow before roasting? Rollo candy work really well for this yummy campfire treat! Reese's peanut butter cups are REALLY good on s'mores too!