Finally! YES!! So happy!
I was going to do a twisting knit stitch (like I did on the plastic bag holder) to hold up the sides. That turned out to be a really bad idea–if I’d kept that up I would have trashed both my hands AND the expensive wooden needles I was using.
So I did knit ribbing up the sides. And not quality knit ribbing either, since while it goes quickly, it’s excruciatingly boring.
This meant that the sides needed to be longer, so I extended the length of the sides using Hobby Lobby acrylic yarn from my stash.
I finished up the sides with a nice tunisian pattern that I’ll be using as trim on future items. You can see it at the front, in the 1st picture.
Later edit–the cats enjoying their new cat bed: