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Depends on the species and thickness of the slab.
Most sawmills these days will slab a trunk any way an then bandsaw to separate the quarter sawn, rift sawn and through sawn timber. Traditional milling techniques are sadly dying out as they are not cost effective.
For example to get the maximum yield of quarter sawn (i.e top-grade) timber from a tree, the trunk must be quartered. Then when cutting planks after every cut you have to roll an rotate the quarter thus requiring more time and labour. Alternatively you can through cut the log into slabs and then season it or kiln dry it this will then allow you to rip off quarter sawn lumber, rift sawn lumber and through cut lumber. It also means less waste.
Unfortunately, you'd be better off seasoning it in sections of trunk before planking it at your friendly local sawmill. Cross sections tend to split like buggery unless seasoned first.