I've had solid luck with a garolite sheet (place I buy from has fr4 on steel sheets), pretty much what I've been using for most prints as it's durable and just works. I use a few drops of a Nano polymer adhesive that I spread thinly over the surface, found it helps with release. I'd actually really recommend something like that over gluestick, less messy, easier to get even and it'll hold, good for a bunch of other materials as well.