Great care needs to be taken when carving to ensure that these checks remain clear of sawdust so that when they close no obstruction impedes them. With patience and proper care when carving, these checks disappear. If you live in an area that has very low humidity the surface will dry out more, and checks may re-open in order to even out the dryness of the object. Patience is needed as it can take some time for this to happen. Checks that open dramatically can be slowed down by placing a damp cloth in the back of a mask.
Some moisture is absorbed in the surface of the wood thereby slowing the cracking action.
In more extreme cases the piece can be put in a tied plastic garbage bag with the slightly damp cloth. Over-night the moisture content will even out and stop the checking. Of course as soon as the object is out of the bag it will begin drying out again. It is a delicate balance to dry the piece out without letting the checks get any bigger. Applying oil to wooden artifacts.