Should I use "are" or "is" in this sentence?
The technical work done at these meetings is an import precursor to the...
You would use is.
The issue is that the "work" in "technical work" is a mass noun or a noncount noun. Rather like "bread" or "advice," even when multiple items are involved the noun form would remain singular:
I have received a lot of advice (but not "a lot of advices")
I have eaten many loaves of bread (but not "loaves of breads")
I have a ton of work to get done (but not "a ton of works")
So even if you are doing a lot of technical projects, you are in effect still doing technical work.
The technical work ... is ...
The technical work done at these meetings is an import precursor to the ....
Subject here is "The technical work" and it's singular - so you have to use "is"