So, from a 1-yard length of black denim and a small box recycled out of a dumpster...
My "policy" with this project is, "it doesn't have to be pretty, it just has to work." I'd originally cut the fabric to only cover two sides, but when I'd rotated it 90°, I discovered it could almost cover 3 and still have enough margin to reach the inside bottom (to anchor it to the box).
The second image is the trial of connecting the hook fastener to the bottom of the box (the floor of my car trunk is made out of loop-fastener fabric, and I don't want the box to slide around) with minimal stitching (in other words, a lot of tape). I've had it get ripped off more than once, and so I went overboard this time.
Image 3 shows the blank canvas (or rather, denim) before adding anything.
Number four shows the completed side one, empty, while 5 shows it filled. It consists of four pockets, each individually sized and customized for their intended use. 1) The back most (base layer) is for new client folders for my personal business. 2) The tall narrow one is for my nylon dog leash. 3) The top one holds both spare animal mess bag rolls and business cards. 4) The loop holds a dog treat tub.
This is all for my work gear, nothing more on this side, and no more gear kept elsewhere.
Part 2 will be for camping gear, like paracord, ground stakes, carabiners, and cooking supplies.
Part 3 is currently undecided (as the third side was unplanned) but may be for medical gear that doesn't fit in my first aid kit.
This shown work took about 6 hours, and the only hand-sewn stitching was with the fastener on the bottom. Design was done ahead of time, but I did a lot of re-measuring, trying to minimize fabric waste.