Why not bake your own bread when you’re camping? Slab bread is bread baking Stone Age style. If you really want to create authentic northern European Stone Age bread replace the wheat grains and wheat flour in the recipe with rye grain and rye flour. The wheat had not come this far north at that time. And skip the salt and taste the bread with wild herbs that would have grown here then, for example, yarrow or nettles.
1 dl [0,2 pt] whole wheat that you’ve cruched
1 dl [0,2 pt] flour
1/4 tsp salt
1 dl [0,2 pt] water
This is what you do
 Prepare all the dry ingredients before leaving home and put them in water proof containers. And remember to bring someting to measure up the ingredients in, if you have packed for several rounds of bread baking.
 Put all ingredients into a bowl and mix them to a smooth dough with your hands.
 Divide the dough into suitable pieces, pat the dough pieces into round and flat bread.
 Place a slab of stone on the campfire. Bake the bread on the slab. You can also use a dry frying pan and a camp stove.