Dieses Regalbrett kann man in allen Farben herstellen.
You need barriers first. You get this with the cheat /give @p barrier
Now you build the barriers on the wall where you want the shelf to be. The width doesn’t matter
Now you pick a carpet color and put this carpet over the barriers
Now you can also put a row of carpets over the carpets
However, you can’t put anything on these shelves. Except for the top… But then the object would float.