tash-LICK, tash-LEEK, TAHSH-lich and TASH-leekh.
I tend to say Tash-LEEK, which rhymes with antique…but that’s probably not exactly right.
My very smart friend Diane Levitt (who swears this is waaaay more than you’ll ever want to know) says:
What you really have here is four spellings of two pronunciations,
from the Sephardic and Ashkenazic traditions.
The ch/kh are two variant English spellings for the Hebrew sound of chet (like something caught in the back of your throat) rather than ch like chair, and the i/ee are variant English spellings for a Hebrew vowel that is somewhere in between.
You only need two pronunciations, and could identify them as Ashkenazic and Sephardic if you want, but you need both or you’ll seem elitist to those in the know.
The real problem is that you don’t explain the ch sound, so people who don’t know will say ch like chair or k like kettle.
I would suggest giving a little guidance on this. I found a nice way to help people with this online, so this is my suggestion:
Tashlich (TAHSH-lich or tahsh-LICH; the “ch” is pronounced as in “Bach”)
See? I told you she’s smart!