There is no doubt that bay window cornices add an amazing elegance to the interior design. If it has a shelf , it offers a large space to place some stuff on it. Therefore building a bay window cornice in kitchen is a wise decision in many aspects.
Building a useful cornice like the one seen in the picture requires plaster material and a mould with a desired shape. The top part should be flat in order to function as a shelf. You can place any stuff on it such as flower pots and something fitting there.