Slipper Time!!!!

At Hospice they want me to whip up some slippers for the clients who tend to have cold feet? Say what? I can't make to things match can I .. and what about sizes? S-M-L-XL I am still working on the size part in my mind as the pattern I found & am currently using is more about measuring the length & the fattest part of your foot vs shoe size..HELP!!!!...

I whipped up a pair for my DD keep in mind she has some special feet issues they are different sizes & different widths around as well due to the surgeries she has had.. Here is what I whipped up... Mind you she made me modify them after I made then as she didn't like the point the heel made at the bottom so i folded it up stitched it into place  and then stitched it closed on the outside (it created a hole gap so she wanted it closed)

Here is the pattern I found