The pot is seen in #476. It is slightly larger than Haley's head. A human children could put their head in that pot and lick most of it clean. Someone with a slightly larger head might need to use their hands or other appendages, or a utensil.

Let's look at which of the more popular suggestions could work you do insist on a small head like an anteater. I believe a Protean could grow a head of a suitable shape. And Uvuudaum is large sized and has a Sliver-like head which might fit, but we're not sure if it even has a mouth, let alone tongue. A Carbosilicate Amorph is only medium sized, so it's possible that his head would fit. A half-green-dragon half-green-dragon half-green-dragon half-green-dragon half-green-dragon young adult green dragon is only large size and has elognated elognated elognated elognated elognated features, so he might actually end up with an anteater-like head with a long tongue. It's just as well, since his overly long claws wouldn't let him get the sauce with fingers. Glabrezu are huge size with a dog snout so I'm quite sure it wouldn't be able to lick the pot clean with that; his hands might perhaps fit though.