Lock in revenue & withdraw lower than cost basis / minimize capital gains tax.. How to do it?

I think this question has been asked in some form but I just wanted to ask a little bit more specifically:

Let's say I have a cost basis of $3K for VUG from a couple of years ago and I want to maintain some position in and withdraw some. Does me selling less than $3K mean I don't incur CGTax? Just asking specifically since I've seen contradicting answers from the search..