I got some 6x6's and deck post brackets that are similar to the picture below, except they're 8" high:
Come to find out, the 6x6 is slightly too large to fit inside this bracket. Now I see how this makes sense. It is better that the bottom of the post is notched off, so that water runs over down the side and over the metal, instead of in between the wood and the bracket.
I'm afraid this will take forever. What is the best way to shave off the bottom of the posts? I have 6 of them and will need to shave off 8" on all 4 sides. I have basic tools, like a chopsaw, skill saw, table saw, but I can't figure out how to do it, except use a chisel. And I'm afraid using a chisel will be imperfect and effect the stability.