This monster box is 30"x20" of usable pooping space with a flat base that won't collect pools of urine beyond the reach of your scoop. The project shouldn't take more than an hour (unless you choose to spraypaint), and only requires a saw or cutting wheel to get through the polypropylene. If you have a cat capable of leaping, you can just buy the bin and be done with it. Otherwise, I'll show you how to cut the plastic and cover it so your pet's tummy doesn't get caught on the raw plastic edge.
A litterbox should be unobtrusive, easy to maintain, and easy to use. This one is all of the above, and I added a spray-painted stripe across the front to indicate to the puppy where the box began. (You can skip that if your pet is a chewer and you're afraid it'll suffer from munching on spray paint.) The clear edge was confusing to my dog, so I added some contrast. Dogs can't really discern red, but differentiating between concrete and the box was apparently tough when the box was the same color as the ground. The red stripe is just a boundary indicator, and it's totally optional. So optional, in fact, that I didn't document it.
Step 1: Supplies
I chose the Ikea Samla 31x22.5x7" clear under-bed storage box. It's big enough for a tiger cub or 30 pound dog. It's squarish shape allows for numerous spins and sniffs prior to use, the walls are high enough to retain litter and prevent animals from squatting over the side, and it's a departure from the narrow under-bed options from Rubbermaid and many other bin brands.
You'll also potentially need:
Step 2: Measure
I left three and a half inches of litter-retaining plastic beneath the opening. I elected not to flare it at the top to make the cuts as simple as possible. It's a pain to cut plastic like this, and right angles make things easy. You can get as fancy as you like, but I found that my dog only cared about the width of the opening and height of the jump.
Step 3: Cut
To avoid binding the disc in the plastic lip as I did, I recommend a hack saw for the vertical cuts and a Dremel for the long horizontal cut. It'll save you some trouble, as the cutting disc of the Dremel doesn't like the folded lip of the container whereas the hacksaw doesn't really like to make 90 degree turns.
You can use either to cut the cord organizer.
Step 4: Finish the Edges
To epoxy the cord cover in place: Start by roughing up the area to be epoxied with sandpaper or a file or rasp. Then apply putty to the inside of the cord channel and snap it over the plastic edge. Voilá. Now you just need to wait.
To paint: I freehanded it without a guard to get that blended overspray look on the sides. I used several coats for even coverage.