Soil blocking has always made me wonder about the whole "only use soiless mix in containers" mantra. It would probably depend on what kind of soil you have available. At my old garden it would probably have been too heavy and dense clay and not good for growing seedlings in. Here it's too sandy and the blocks would crumble like pouring water on a sandcastle. But, I do believe soil blocking is the method that is described in "The New Seed Starters Handbook" by Nancy Bubel. If I can find my copy, I will take a look and see what it says.

One thing with the rock wool is that you would have to buy it new every year. You could also try peat pellets. Again, you'd have to buy new ones every year and according to a great many people you MUST remove whatever it is they are wrapped in before you up-pot or plant them out since it does not decompose and roots cant grow through it. I've never used these myself but there are a few scattered around the yard from the guy who lived here before me and they are still perfectly intact so the reports are probably true.

I love starting seeds. I hate taking care of seedlings for the seemingly unending months of cold before they can be planted. Then, as soon as the weather seems like it's going to be nice and you are nearly done hardening them off, they have to back into the house for another week because of a spring snow storm.