flour on top of the sourdough potato bread

It does have an elegant look to it, doesn't it.  Just proof your loaf in a round wicker basket, or something similar.  You should be able to find something perfectly suitable in a dollar store or thrift shop.  Line it with a cloth and rub flour into the cloth.   Once proofed, turn it upside down onto a baking sheet lined with parchment paper, score it with a # sign (or as preferred) and bake. Now I'm a novice, so others might be able to improve on those directions, but that's how I do it, with decent results.

Karen

The coiled baskets are made of either plastic or wicker. Both work well if dusted with flour so the dough doesn't stick. You can use a cotton tea towel dusted with flour in a bowl to proof a boule in but if you want the coil lines, you will need to get a coil style basket

It is a nice effect. There are several places where you can buy the baskets. Here is the supplies page at the SFBI site. Very good price and they have several kinds.

Eric

There's a long thread on this site on where to get proving baskets on both sides of the pond here