My question? Would a very simple box cut it? I'm talking 36x18x24 basically
... so I was considering rabbeting the edges and using wood screws to put it together. Outside of that, my woodworking guru says I should just "do it right" and use tenons and such.

Your thoughts?

-I've looked at mine from Ikea and it seems to be knocked together from something like MDF with triangular cleats of mystery wood holding the inside corners together. The top is not hinged but just sits on the box with four rubberish pegs sticking down so it seats square. Works great and would take about an hour to build, with plenty of time left over for standing and staring at the thing. (Can never get enough of that.) For me, strength would be enough here. Sure, if it were a Queen Anne footstool or something... but a cube of upholstery, who cares?

-If the whole unit is going to be covered with fabric then fast & cheap is my thought. As long as the unit is strong and durable to your satisfaction I think your fine.

Plywood might work for you too, saving having to joint, biscuit.