Once I saw that Lindy Smith doesn't carve the hole, I never looked back.
I had so many issues with that flippin' hole--the "wall" sliding off, not making it big enough so it cracked after I placed the top tier on, and just being more work than necessary--I was happy to see it works just fine without it.
I do find that both the top and bottom of the tiers need a slant so they aren't protuding out to one side. A wedge shape (except for the bottom tier).
How I do it: I glue 4 foam core together for the baseboard. This way I have a good support base when I hammer the dowels down into them. Each tier is also on foam core board. After I stack the cakes as I normally would (using a small amount of piping gel to help hold them in place), I hammer 2 long dowels all the way through all tiers down into the base board.
I traveled with the following cakes fully assembled and they were perfect upon arrival.