The joinery here is pretty simple, a couple of tenons and some big lag screws. Because the top is split into two slabs and has a gap between them to hold the tool trays there is a need to really make sure that the slabs won’t move once they are attached to the base. If the slabs move at all it will throw off the vises and make the gap inconsistent, which will either cause the tool trays to get pinched and stuck, or fall through the gap.
Because I sometimes have a friend, or my daughter, in the workshop working on something or helping me with something, I have installed a vise on the back slab of the workbench as well. Both sides of the bench will be accessible to work from and for some of those larger projects I may end up going from one side to the next while working on different steps of a project. I decided to install a large face vise for this purpose as I’ve already got a leg vise and a tail vise. Time will tell if this is the right decision.