Box Joint Construction

Hi everyone, this is my first visit and my very first post on any forum.

I live in Montreal, Quebec, Canada and although I make furniture my main area of work is re-finishing.

This is my problem, I have designed a coffee table that is essentially a box (approx.. 20"x40"x6")that sits on a pedestal. I would like to maintain continuity through the entire box (top, bottom, and sides) by using Box Joints to join the pieces cut from a single sheet.

After much research I have found many jigs for table saws and router tables. However, and I haven't tried this yet, I can't see how I can balance and maneuver a 20" x 40" sheet on a table.

So, is there any other practical way of cutting this joint at the end of a long board with a jig and hand held device?

Thanks in advance, Tony