Some people carve or I've read that you can use different sizes of cakes so have a 6" on the bottom and an 8" on the top - still some carving needed probably. You can google "tapered cake" I got this -
here's another forum thread with tips on making tapered cakes:
DanaG21 beat me to it! Good luck, hth!
Here you go...basically...size 7" cake board on bottom, another cake board 5" over that, and slice board to board knife touching board.....crumb coat cakes when done, let dry....turn cake over....tapered cake