Trim the crusts from slices of fresh bread and arrange the slices in a single layer on a baking sheet. Bake the bread in a slow oven (250° to 275°F.) until the bread is very dry, but do not let it brown at all. When the bread is dry, crumble it in a blender.
If no blender is available, put the dried bread through the fine side of a grater, or put it through a food grinder.