Call me slow, but I just discovered this technique this year. I think it’s awesome. No purchasing individual pots. Once you have the soil block maker(s) and trays, there’s no need for further investment to start seeds.
I like Eliot Coleman’s explanations with their soil block recipe and soil block makers (including cheap homemade). For us, I won’t be adding blood meal or rock phosphate since we make vermicompost at home, adding rock dust, pumice and egg-shell for the worms. I’ll be adding enough vermicompost to compost ratios. Instead of peat moss, I may get coconut coir.
Here is the soil mix recipe:
Here is the piece on soil blocks, including making your own:
A piece on soil blocks in cold frames:
Germinating pepper plants in soil blocks: