This year, I invested in a couple of seed blockers to start my seeds: rectangular moulds divided into small compartments that are pressed into the seed-starting mix, then the blocks are ejected into a tray and seeds are planted into them. The smaller seed block create 15 3/4-inch soil blocks. The larger blocker, for larger seeds, creates five 2-inch blocks. Getting the soil blocks was a strategy to reduce costs and avoid plastic -no pots required. Also, by using the smallest size blocks, I can start 300 seeds in one tray and fit 2 trays on the heated mat, speeding germination of 600 seeds at once.
I ran into one complication with the blocker. I intended to use Eliot Coleman's recipe for seed starting mix, but it called for "green sand" and I could not find that anywhere. I ended up concocting my own mix, with organic potting soil, seed starting mix, and compost. (approximately 1:2:1), adding water until a handful of soil would hold the shape when squeezed tightly. That mix seems to be working just fine.
A second tray of tomatoes was started a day later on March 1st -- this is how they are looking today. Not quite so leggy - I think they appreciated being moved under the lights sooner.
The crazy thing is that I am starting my seeds at the appropriate time to be able to transplant outside on our traditional frost-safe date, Mothers day, almost two months away. But we have 80-degree weather right now!! The weather is just too, too weird these days.