I understand what it means now, thanks, cuchufleteI've heard it used two ways, both in appreciation of something, and as a highly sarcastic
condemnation. I learned it from a native Alaskan who had been living in Minnesota for decades. Both areas have lots of deer hunters. So much for the thin etymology.
Here are two examples, to illustrate how it might be used:
Praise: (Note that 'slick' is colloquial AE for very good.)
Young man shows off the elaborate stereo system in his rusty car to a friend. There are speakers everywhere, and the sound it produces is deafening.
Friend: Wow! That's slick as deer guts on a door knob! (Meaning: I'm really impressed! It's great!)
A person appears at a party wearing a green shirt, orange necktie, light blue trousers,
and white boots. She has a pink hat on her head. The hat is decorated with multi-colored flowers and plastic grapes and cherries.
Person: Hi Reginald. How do I look?
Reginald: Hi Marcie! You look slick as deer guts on a door knob.
Caution to non-native speakers: Don't use this expression unless you are in Alaska
in deer hunting season, and know all the people around you very well.
Yes, that's the third meaning of the expression: very slippery, elusive, evasive, deceptive.
Given that variety of meanings, and the vocal and physical queues that distinguish one
from another, it's a dangerous expression to use in person. In writing, where context
helps out a lot, it's safer.
For the intensely slippery meaning, it's something like another very colloquial expression I once heard, but have never used before: He's harder to catch than a fart in a hot frying pan.