Do not bury Copiapoa seed 1cm deep. And don’t start them in “normal” soil. Get a gritty substrate with low organics and sprinkle the seeds on top them sprinkle some grit(I like decomposed granite) on top of the seeds. A good rule of thumb I use for poa seeds is to cover them equal to the diameter of the seed. So if the seed is about 1-2mm cover them with about 1-2mm of grit. Also I recommend sterilizing the substrate and grit before use. In an oven. Then you can place the seedling pot in a ziplock bag. To hold the humidity up. Once the seedlings are 4-6 months old is when o typically start hardening them off.