Similar in purpose to a banneton, a bread couche is a bed made of fabric for shaped bread dough to rise in. It is used for bread that is baked free-standing, not in pans.
It helps the dough keep its shape while proofing and rising, and allows the dough to be easily transferred to a baker’s peel for transfer into an oven.
You can think of it as an ambulance stretcher for dough.
The fabric used needs to be fairly stiff, such as canvas (some people use the legs of old jeans.) You create rows or channels separated by folds with a separate loaf of bread dough in each one, letting the folds keep the dough separated.
Bakers never wash them.
Never put the couche in the oven.
“Couche” means “resting place.”