I love growing in my raised bed veggie gardens and sometimes the slugs love my veggies too. The smaller the starts, the easier they are to be destroyed. So last fall I found some copper tape on clearance and figured out that the roll contained just enough to encircle two plastic “flower boxes” and enough to surround the drainage holes on the bottom. This has been very successful! I have basil and a few lettuce plants that are growing in this prime real estate. When I want a few lettuce leaves to put on a sandwich, I do not want Swiss cheese lettuce.
The Transplanted Gardener 
hi! try adding a thick layer of coffee grounds around the perimeter of your flower boxes (kinda like a wall) the granules are too course for the slugs and they don’t like crawling on them. Happy Gardening!
Thanks! I will try that around my bean plants in my raised beds. Good tip.