In the IPA chart, there are some white areas with no text. These are where a sound can exist, but it has not been found in any known language. (The gray areas are where humans are incapable of making that sound.) I was looking for sounds to try, and one stood out to me: a bilabial approximant. I would like to know how to position my mouth and what the sound is the most similar to. If it exists, I would like a link to the sound.
The letter [w] is classified as a labial-velar approximant, meaning that in addition to being bilabial, it has a velar approximation. There is typically no empirical evidence provided for the articulatory properties of the letter "w" in a language, though given that "w" is generally considered to be a non-syllabic variant of [u] and it is much easier to establish a raised back tongue position for [u], "w" is honorarily labeled labial-velar. It is quite possible that there are languages where the labial glide has no tongue-raising component. What we might say is that there is no language which contrasts two kinds of bilabial approximants, one with and the other without velar approximation.
However, there are many Bantu languages which contrast "β" and "w", but where furthermore "β" is acoustically distinct from the kind of "β" encountered in Ewe or Spanish (an example is Logoori, another is Karanga Shona). This means that some new synbol is necessary for phonetic description – except of course this is a question that should be approached using experimental physiological methods, not impressionistic auditory guesswork about the underlying physical state. So this is an area where we just don't know what the tongue-facts are in all cases of "w".