Coat a large sheet of tin foil generously with oil cooking spray and set aside ensuring it is completely covered, including the edges.
In a large mixing bowl, combine the oats, oat bran, cinnamon, sea salt and mix well. Add the oil of choice.
Lay the mixture in the centre part of the tin foil, preferably in a single layer, ensuring there is sufficient room to around the edges to wrap.
Wrap the granola up without any room for air- We don't want steamed granola here. Lay the foil patch on the heated stone/coal and allow to heat for 5-10 minutes. Using tongs, shake the foil pack roughly every 2-3 minutes to avoid sticking.
Remove and carefully open and allow to cool for 5 minutes. If you want melted chocolate and marshmallows, add now and mix through and allow to cool.