The logo on the carbonized Pompeiian bread

[Arahne]

I have few ideas. I think that most important thing is not to use a lot of germ in such bread. Maybe something like soda bikarbona was used. Second is my mothers and my experience for creating bread for slava (orthodox serbs differ from other orhtodox nations for feast called slava-every familly has its own slava i.e. they celebrate their saint, mine is st. Nicholas). So, my mother creates small grapes, books, birds, and proskurice (this is how we call those small stamps with Christ's name that Stefanos spoke about). She makes them with mixture of flour, water and salt (like when you create noudles without egg). And they always look like they looked before baking.
And you always have these crustuli that are much more complicated.