Back in the 1980s I had a small long bed pickup with a shallow fiberglass camper shell on top. Didn't everybody have one of those back then? My friends had "carpet kits" in their pickups. Instead of buying an "expensive" carpet kit, I just copied theirs to save money. They were made from cheap plywood, 2x2s and 2x4s, with foam and carpet on top. I used a circular saw, screws, and a friend's upholstery staple gun to make it. No skill or talent was required.
It had two long side boxes that covered the wheel wells. The side boxes had internal dividers, making storage compartments in front and behind the wheel wells with hinges on top for lids. The wide center area had two platforms front-to-back. (It could have been one very long platform, but two were easier to manage.) They rested on 2x4s bolted along the lengths of the side boxes. You could easily lift the rear platform like it was hinged, to expose the large middle section "storage area."
The carpet kit formed a comfortable, full width bed across the back of the pickup. The top was a few inches below the height of the rails and tailgate, barely above the wheel wells. I kept water, canned goods, backpacking stove, sleeping bag and pillow, and other camping gear in the storage compartments. It also served as my "earthquake emergency kit." With all that storage, my stuff was always out of sight.
When I was young and single, I traveled and camped. I could leave on a whim, without bothering to stop at home after work. I never bothered with motels - the carpet kit was very comfortable.
If you search for "pickup truck carpet kit" images, you should find many examples.