A lot depends on the dough's water percentage. A very wet dough, 75-80%,
will be soft and more difficult to slash than a firm dough. I have found
that lames and razor blades are not very useful with such breads, and since
I saw Jaques Pepin use a serrated-edge knife for this purpose, I use it all
the time. Cuts through dry or wet loaves very nicely.
I like to make shallow slashes, which expand a bit on the surface and
result in the slashes taking the form of lighter-colored areas on the crust.
Max Prola