I agree that sowing direct doesn't always work. I start everything off in pots or trays and plant them out later. Even plants that are supposed to be sown direct, such as annual poppies, can be successfully transplanted if you're careful. I can only imagine direct sowing working on completely bare beds (i.e. no competition for light, etc., from established and regrowing perennials and shrubs). And yes, slugs will love the soft young growth of many seedlings. Incidentally, I've successfully managed to keep the slugs out of my small vegetable patch by edging it with copper piping. Apparently the copper gives them an electric shock so they won't cross it.