'Silky smooth' and 'buttery'. "Teflony'?
This question had been asked in different forums in the past.
AnswerBun or AnswerBun
Stackexchange
And a specific answer has not been found. There are some phrases that can be used to mean the same thing. I am providing some suggestions below as the original questioner in each forum was unsatisfied with the provided word choices.
Super-phonatives (Interestingly I could not find "phonative" in dictionaries, it is a commonly used term in medical sciences and it generally means the ability for phonation and/or the process of phonation)
Super flowy words (Flowy means which that flows, and flows easily)
Words that glide or tongue gliders
Superfluid words
From Brittanica
superfluidity, the frictionless flow and other exotic behaviour observed in liquid helium at temperatures near absolute zero (−273.15
°C, or −459.67 °F), and (less widely used) similar frictionless
behaviour of electrons in a superconducting solid. In each case the
unusual behaviour arises from quantum mechanical effects.