Question
What is the best way to protect veges from snails , slugs and slaters/centipedes organically?

Answer
We discovered when we lived on San Juan Island, slug capital of the world, that the only sure way to keep them out of the garden was to line our entire garden perimiter with cedar sawdust  along the fence line, and make a little dent in the middle of it and fill it with rock salt.  We also put a little 1 x 4 board "roof" over the mound of cedar to keep the rain from washing it away.  This was attached to the fence posts. This stopped any new ones from entering into the entire garden.  For centipedes, they did not seem to do much damage anyway.  It is the slugs and snails that are the big problem.  This was that we discovered was 100% effective.  Then all you have to do is get them out of the actual garden, which you can do with boards, which they will crawl under at night.  In the morning you just scrape them off outside the garden.  Every other way we tried failed. When we sold our gardens, they were slug free.