Flour base: A blend of rye and wheat flours—rye is usually at least 20% by weight, often more.
Leavening: Traditionally made with sourdough starter; some recipes add a bit of commercial yeast.
Fermentation: Long, slow fermentation develops complex flavors; multiple rises and/or cold proofing are common.
Crust & crumb: Crust is thick, rustic, and often floured, while the interior is dense yet tender and flavorful.
Optional flavorings: Caraway seeds and other spice blends (e.g. speckled with caraway, coriander) are regional touches.
Shape & scoring: Typically round or oval, baked freestanding, with natural cracks or scored patterns.