well the subject seems to be building a frameless box and that takes some material with some structure strength, enough to attach it to itself, anyway. And very thin panels make that difficult without some sort of frame. Be it angle iron or 1" square tubing. There's got to be some sort of minimal framework to hand really thin panels from. Elsewise you are going to wind up with something very heavy made form 3/4 plywood and some form of pocket hole joinery like a Kreg jig. And while heavier, such a thing might be strong enough overall without being TOO heavy*. And then you just need to laminate the exterior with something waterproof, be it metal, fiberglass or some form of HDPE.
3/4ply is a 1.75-2.25#/sq', call it 2# and mentioned earlier a box on a full size is at least 400sq', a midsize might be 300. So you are burning a lot of load capacity just for an empty shell.
It all seems like a lot of effort when there are 'off the shelf' structures that hinge open or pop-up or things like ground tents with a fly that attaches to the rear end of a camper shell or the like.
Cheap, Light, or Easy, pick one and only one, because you aren't going to get two of those choices at the same time. Unless you want something really crude or really ugly.
A very long time ago I 'camped' in a dry lake bed waiting for a space shuttle to return to Earth, with little more than some thin-walled PVC sprinkler pipe bent into hoops stuck in the stakebed holes of my pickip, with a blue tarp bungee-corded over the hoops to the bottom edge of the bed sidewalls. It was very ugly but it kept the cold wind off.
We've got a member here, in Alaska or the PacNorthwest IIRC, who's built his own big box on an old GM pickup. The back is highly angled and IIRC forms a loading ramp of sorts. I always thought of it as 'the Poor Man's Landmaster'. I think he skinned it in sheet alumnium, too.
And also a long time ago I built Arty Fire Direction Control CPs in the back of 5-tons using 2x4s and plywood. Ugly as hell but they did the job. Not enough unit funds for the pre-built shacks the Army used.
But thin very costly panels with no frame. That's 'SpaceX' ********. If one has the budget for that, one has the budget for a ready-made product.
