How large are you talking about?
This Live oak log was 52" across at the widest and was 12" long--I sliced three 3" cookies and one 2" from it. Three of the slices I coated both sides with three coats of anchorseal--this was in 5/2004--They have not started checking to date. One of the 3" slices I took in my shop, fresh sawn (green) and planed flat with my router, then sanded to 150 grit, occasionally wiping with denatured alcohol to slightly dry the surface to aid in sanding. I did some research on which epoxy would have the least blush if I trapped the moisture in and found Jamestown Supply,( jamestowndistributors.com ) and used their Mas Epoxy. I put 3 coats on all sides including bark. When dry I set it on an old feed store dolly that I had welded some risers to in my livingroom . That was in 2004. I had no cracks until this past year, one large crack has formed in one of the trunks. My plan all along has been to slow the drying down as much as possible (3 coats of epoxy) and when it is completely dry--aclimated to my living room--then I will take it back to my shop and sand it down and fill the new cracks with epoxy and refinish it properly. I do not know what difference it made in the cracking that there were 4 trunks inside this one tree. My advice--let it crack and then fill with epoxy.
Good luck, Bill