Favia Brain Coral

[jcmjoe]

So i picked up a very pretty Favia Brain coral, I hope this doesnt sound like a dumb question, most of the time I see these on the substrate. Do they grow into the half sphere "brain shape" or are they generally on a rock that they just cover, I have it directly on the substrate bottom. I kinda thought they grew into that shape as they got big. Thanks for any help!