I haven't, but I want to. It should work the same way. my problem is that I keep seeing the same tutorial (with triangular sides folded down, but that's not what I want to make.
I'm thinking of making a pattern for the size box I want in heavy pellon, cut fabric a little larger (enough for seams), do same for inside. Sew the pellon to one side of fabric (outside or inside --I don't want iron on because it crinkles after washing). Make the other side, sew them together like a pillow, leaving one side open to turn, and then ladder stitch that shut. Then tack corners of inside to the outside of the box.