I've never gone to much work other than cut square and attach anvil, but here's what a local smith does here.................
http://www.blksmth.com/Anvi_base_preparation.htm
That's an EXCELLENT short course in prepping a stump for an anvil.
I've tried pretty hard to wear out quite a few anvils of different types and sizes, mounted on a variety of different stands; in my never-humble opinion, it's purty hard to beat a stump.
My PW shop anvil is mounted on an oak stump; didn't do a thing to prep it, other than saw it off plumb/level, top and bottom, with a misery whip. The chunk I chose was the base three feet of the trunk, beginning right above the root-lift (given the multiple twists in the grain, it's not real prone to splitting); it had already pre-seasoned for several years, with the bark off.
Once sawed off plumb and level, I wrapped it with a couple 2" wide steel bands (bolted tight); welded some 1/2-round loops to the top band for frequently used tongs and hammers; and strapped the anvil base to the top deck of the stump.
Good enough for this ol' hoof-butcher... but then again, I don't do any super-heavy ironwork anymore, either: no "smith and striker" work.
Having wrecked my wrists and elbows several decades ago, working with anvils too high and hammer handles too long for me, I'd strongly suggest you put some serious thought into anvil height: it has far more effect on the quality of your work than it first seems.