bank-teller

Spell it out.

BANK:
I notice than when I spell "bank," I leave out the "A." (Unless I sign really slow.)
This is what you call a "lexicalized sign."  Meaning, over time the spelling has changed and taken on the aspects of a sign.  In this instance, the letter "A" has been "dropped."

Or it might be argued that the letter "A" is being done with the pinkie and the ring finger at the same time as the letter "N" is being done with the middle and index fingers.

Either way, the important note is that skilled signers recognize the "lexicalized version B-N-K as expressing the concept of "a place where you store your money and get loans."

Why in the world would you need the sign "teller?"  If I want to tell my wife about something the bank teller said or did, I would simply sign, "WOMAN IT B-N-K..." or "MAN IT B-N-K..."

If I am a bank teller and need to tell someone at a party what I do for a living I'd simply sign, "I  WORK  B-N-K" or "I  B-N-K  T-E-L-L-E-R."