Yes, logs will eventually split themselves, as will stave splits left with the bark on.
The more you reduce it, the less likely that it'll check, so long as you seal the back and ends. But, if you reduce it too far, it may move to the side as it dries, forcing you to heat correct it. A happy medium then works best.
Take the log and split it into pieces that are about 3" or so across the back. Then, with woods such as osage where you remove the bark and sapwood... get the bark and sapwood off as soon as possible and immediately seal the back and ends. I also like to reduce the bow in width down to about 2" wide, and in thickness to 1" or a little less... leaving extra for the handle of course. Wood can be dried and kept this way indefinitely without worry about checking... as long as the humidity doesn't vary too much.
For whitewoods such as hickory, ash, elm, hophornbeam, etc... split the logs down into pieces 3" across the back, remove the bark, reduce to 2" wide or more and 1" thick or less and let them dry. You can seal the backs if you like, but on some whitewoods, it isn't necessary.