My cousin's fiancee is looking to build a bench for their kitchen. From his description, it sounds like what I would call a "slab bench." Just three thick slabs of wood, two for legs and one long one (about 60 inches he said). He hasn't decided on a wood. I recommended hardwood, but in retrospect given the thickness of the slabs, I think it might actually be worth trying in pine.
I told him I would typically use a frame or angle braces to prevent the seat from bowing and to make a rigid connection from the legs to the seat, but if it's a thick enough slab maybe that wouldn't be an issue: Is a 3-4 inch thick slab enough that it won't noticeably bow?
If they were to not use angle braces or a frame (i.e. there are only 3 members, no supporting structure), how should I connect the legs? I thought maybe just a really big mortise and tenon for each leg would do it, but I'm still concerned about it being weak. Should I just tell them to suck it up and reinforce the connections?
edit I've been provided with a reference picture of what he's looking at. It looks like it's just reclaimed 4x4 lumber with a miter, ... maybe biscuits or something as well, but no braces or anything.