<----- Hey Look I GOT WOOD
I agree with Tsevg9 fat down on UDS.
I also agree with Chezmatt, in my vertical water smoker you have that barrier between the heat source and meat. Most of the heat is in the top of the smoker where it escapes via the vents. That said Fat side up.
It all depends on your cooker and your preference.
I have cooked a few briskets and have never needed to turn them. Just low and slow until I get the desired bark and then foil.