Been there. Done that. Have the t-shirt.
I agree that the ripping and planing idea is not a good idea. Each
piece will be heavy and hard to manage. You'll get sniped. Even under
the best of circumstances, machine planing doesn't make a thing flat.
It makes a thing parallel to the opposite side. You'll end up with 3
untrue surfaces which you'll hope to rejoin into one true surface.
I've done the #7 thing. It's a good start if you have a good tool, work
diagonally and occasionally switch 90 degrees to the other diagonal, and
use winding sticks to watch your progress (both in terms of twist and
width flatness). I agree that scraping would be a good preliminary
before beginning to hand plane. Planing something this wide diagonally
would be hard for me as I'm neither tall or long-limbed. When I did it
to a 2'x6', I failed to watch width flatness carefully enough and
somehow ended up with a 1/16" crown. Otherwise, the top was very level
lengthwise. I lived with that for a few years, before doing the router
Router sled is demanding to build. The long rails (length of your top+)
must be ultraflat, at least after they are attached to top. Winding
sticks are again necessary when attaching/clamping long rails to your
top before routing. The sled rails (width+ of your top) must also be
ultraflat. Because the sled rails only contact the long rails, they
must have enough bulk to not sag under pressure of router weight and
your pressure on the router. The instructions I've seen don't tell you
to build in dust clearance, which is important because you lose flatness
if the router baseplate rides over the dust you're generating. I was
careful in building mine, and everything worked out nicely. I didn't
have to remove much material because I only had a crown to take out.
Still, it's a big job to build the sled. [Accuracy of the result can't
be better than the accuracy of the tool.] I built mine with the idea
that it would be useful for other things (like table and dresser tops),
but that turned out to be idealistic (thus far). Those kinds of tops
are thinner and harder to attach to rails; they also have more internal