I think I can hack the carving part. What I am worried about is the fondant. I do mostly all buttercream cakes, but I realize this one needs to be fondant.

The pillow cake instructions on this site uses on large piece of fondant to cover the entire cake. I've watched a youtube where she covered the bottom half then flipped the cake to cover the top half.

Which way is the best????

Lindsay Smith says to do it like the youtube video. It will give a much better better finish if you do it in the two parts.

I have no experience with pillow cakes but I have worked with fondant. I think it would be way easier, less stressful to do it the way they're suggesting, in two parts, top and bottom then cover the seam with a nice rope or even just a rolled piece of fondant. You could even use real fabric trim if you're sick of fondant by then

I don't work with fondant a whole lot, and I was worrying it was going to fall off the bottom due to gravity! Surely it will stay glued to the buttercream underneath?

Don't worry, if you attach it with buttercream or ganache, it'll stick just fine.

It is VERY easy to attach fondant to a pillow cake in two pieces. I haven't tried to do it with just one piece but it would seem that it would be very awkard. You have to put an embellishment there anyway so tht it looks like a real pillow, so the seam is super wasy to cover. You can even do a two tone pillow in contrasting colors and designs!