Hi, i've been working on a project in which i'm turning my squier bronco bass into a fretless. and i'm putting little pieces of walnut in the fretslots instead of woodfiller, and my question is this. Would Elmer's glue hurt the fretboard or neck if i used that to glue the strips in?

I would recommend using Titebond wood glue. Also make sure the filler strips are the right fit. If they are too loose or too tight they will effect the straightness of the neck. If they are too tight and you are having to force them into the slots you will promote a backbow in the neck, and too loose of fillers will produce the opposite.

You will want to relevel the neck after they are glued in and had a few days to settle and dry fully.