I always plant mine at the same depth as they were in whatever they were growing in (pots, modules or whatever) so the compost they are in is only slightly buried. I find that putting a thin layer of soil over potting compost does help with stopping the root balls drying out.
Do you take them right out of the growing medium to plant them?
Well . . . that would be the "lot to learn" part. I've successfully grown a lot of things, not so much with onions.
So, my plan is to chit the seeds, and as they sprout, put them in a nursery pot (community pot style), with some distance between plants, to grow into transplants. Maybe 50 seedlings to a 2-gallon nursery (community) pot? My thought is, get them to a decent size in a community pot, remove them from the pot when they are large enough, trim the leaves and get them in the ground quickly (treat them like transplants that you might buy, which are usually bare root). I would probably leave any compost on the roots when transplanting. Seed packet instructions say to sow the seeds 1/4 to 1/2 inch deep, but that's for direct-planting. If the chitted seed, placed in a nursery pot, is covered by 1/4 inch of soil, I'm assuming that the soil over the seedling roots in the nursery pot would be no more than 1/4 inch. In that case, would you only have the roots buried 1/4 inch after transplanting in soil outdoors? Or bury a little deeper (and by how much approximately)?
Or am I going about this all wrong?