If we inverted the last letters of “possible” to “possibel,” that wouldn’t really match how we pronounce it
I’d probably try to read it as something like “possi-bell”
But our actual pronunciation is more along the lines of “possi-bull” not exactly, and I feel like different dialects might maybe lean more towards the last syllable being more like bill, ball, or boll, but I can’t really imagine any dialect where the pronunciation would match a “bel” spelling.
It’s sort of an unintentional half vowel sound that just happens after making the “b” noise, and not really something we’re intentionally trying to put into the word.
Linguists probably have some specific terminology for it, but I’m no linguist.
I don’t think it’s really a schwa, at least not the way I say it
A schwa kind of comes from the back of your mouth like you’re saying “uhh…”
When I say possible, that last sound feels more like it’s the little burst of air from the b sort of fading into the l sound
Then again I’m no linguist so I could be out of my depth trying to really describe the noises I’m making, and I’m not very well-equipped to separate how I talk from more general American English (I’m from Philly, and we have more than our share of little linguistic quirks, after all, we pronounce “water” as “wooder”)