Hi Peter,
I would oil and beeswax the wood immediately, there are several traditional formulas for this, but you have the idea, slow the process of drying down. The oak will service your needs in the interim, but is the least desirable for the purpose you intend. Oak stains and reacts with different metals in different ways, and even with treatment this species has a tendency to check and split really easy. Traditionally a species like elm would have been used as it presents as the very best for resistance to splitting, so you
should keep an eye out for some. I would also suggest you "banding" in a traditional way if possible your stumps. This was common for anvil stups and silversmith stumps that are of a species that split easy. Sweetgum is another species that i have seen used with good results.
Regards,
jay