This is a corrected version of Patrick Zimmer's (dedj on Thingiverse) design. His was a dream come true on paper but was not usable once printed, so I modded it to give a little wiggle room while maintaining a snug fit; the model also had some holes that I patched.

Use your best judgement when setting up a slice profile. I had best luck when angling the flat side it back at a 45 degree angle away from you and upright (3 holes at top end). Most people who are experienced will know what to do anyway.

original design by dedj [ https://www.thingiverse.com/thing:5249378 ]