To Lu-Max, the OP, since you're not planning on using the stump itself as a table but only as the support for a wood (or metal table top), then Bill's last option in post #16 is the way to go:
"If you get it down below the level needed, and it is rough and uneven, you can just screw 4 long and widely spaced lag bolts in until their tops are level, and use these to set a top on. Then take 4 more lag bolts and put them through the top and screw into the stump, to hold the top down. It's like leveling bolts for a steel column."/I]
Fast, simple, doesn't require any specialized tools or jigs, and is the least likely way to hurt yourself accomplishing this task.
However, if on the other hand, you're looking for an excuse (I mean, "reason") to acquire some new tools and/or experience and expertise doing something with wood that you haven't done before, then you have a lot of other ideas to choose from in this thread.
It really depends on what's more important to you - having a tabletop without making it a major project so you can spend your spare time on your "real projects," or learning-by-doing. The end purpose you describe isn't really for a "Fine Woodworking" piece of heirloom furniture - it's for an outdoor table!
If you already had a chainsaw, I would say you could use it to get the stump top closer to level, but you're still either going to have to do a lot of work to get the stump top itself actually level or you will be doing some shimming and adjusting anyway. That's why, for pure practicality's sake, I would go with Bill's suggestions in post #16.
(BTW, the first time I ever used a chainsaw, a friend's small ~18" homeowner one, we were fooling around and helping him cut up a small 8" diameter tree that had died and fallen in his back yard that backed up to some woods. After we cut the trunk into 24" long sections for disposal, I was just fooling around and pretending to be one of those "chainsaw artist" guys you see who turn a tree trunk into something like a grizzly bear in about 20 minutes before your very eyes. Anyway, I was using just the tip of this little homeowner chainsaw to start cutting in the surname of each of the families who were over at the guy's house that afternoon. I was surprised to find out how easy it was to do - really intuitive and very simple and quick. In fact, it turned out so well, that friend just left those three logs with the family names carved in them in his backyard for his kids - all of our kids were about the same age and good friends, so it served as kind of a testament to the friendship between the three families.)
