Thanks for the information! I would have thought slugs would just go up and over a cup circle, but if it worked for you, I just might try it!

I've got several things I only grow in off-ground containers (sunflowers and bok choi) because the slugs mow down the seedlings before they can even get started. I've tried everything up to and including a circle of Deadline (nasty stuff) right around each plant. The slugs just crawl right over it. I'd love it if this worked!

I think it works because that plastic is slippery and they perhaps cannot climb up. Before I did that, bunch of my small plants were eaten up and I thought it was cutworm until one morning I caught the slugs in the act. I have several seedlings still intact for few days now.

I had the same issue this year (first time) and used the same solution, successfully.-- used cardboard tp rolls, cut in half.
For me, I think it was also because I had mulch too close to the seedlings, so I took that up too.