I hear old used motor oil is a great wood treatment too. Obviously not for a dining table, but it will keep that shed from rotting. The problem I see with slabbing, well one of the problems, is you really need heavy equipment and lots of space. Cutting the slab is only half the battle. You also have to find a decent old growth log. Move it, usually several miles. Possibly cut it down. Then move and stack the slabs to dry. Let them dry for years in a covered shelter. If you get all that sorted you might as well take the next tiny step of making it a full time buisness.