I remixed this from Shapespeare's Skull Bowl. I lowered the top edge, so it wouldn't curve in as much at the top. I added drainage holes, and added feet on the back so it would sit level. I also smoothed out the bottom some so it would print more easily and the supports would be easier to remove.
If using the file that has tree supports, make sure to add regular supports as well.
We had some trouble with the large nubs on the bottom printing correctly, so we added tree supports in meshmixer, and added regular supports in slic3r.