Despite scant archaeological evidence, two methods of fire-making could be reconstructed as working procedures:
A quartz-bearing stone (e.g. flint) is used to knock off particles from a ferrous sulphide (pyrite). Caused by the high energy and heat sparks are produced that are caught with a dried strip of tree fungus. Now blow carefully and wrap the smouldering strip (tinder) in an easily flammable material. This can be dried reed grass, a piece of birch bark, or dried bulrush. Under air supply a strong flame will be created.
Another method of making fire is „fire drilling“ which requires a little more practise. A debarked spindle stick is quickly rotated on a fireboard with a bow drill. The resulting wood dust begins to glow and can be used to ignite the fire with a dry bundle of grass.
In both cases it is important to keep the resulting flame alive on the fireplace with easily ignitable bark and thin wood.