I have read accounts of southwest desert people first grinding them in stone depressions with a rock and then putting the flour into depressions in the sand and pouring water over them to leach out the tannins relatively quickly. I have seen old photos of this. I think they did it this way because they didn't have the luxury of running water in the summer months. I'm not exactly sure, but I have seen some of the rock depressions they used. They then baked or fired the flour into a biscuit.
I have read that white oaks have less tannin than black oaks.
I have tried them raw and they aren't too bad at first, but I can't eat more than one of even the mildest I have found unless leached. They are very bitter and astringent otherwise, but they do seem to crisp (if that makes sens) and freshen the breath. It's been awhile. The tannin aspect seems very distinct from a sweeter much more subtle potential taste.
I would ideally keep them whole in a slow moving stream, checking one everyday, until palatable. Then I would eat them raw or ground and mixed with berries and maybe a little wood ash (binder?) and pressed into cakes and fired to maintain shape and keep and perhaps to improve flavor as well.