The last 2 years, I’ve used 3 oz plastic bathroom Dixie cups (2-inch top diam), with 3 cut-holes around the bottom edge. Found a decent potting soil at a local nursery store, loosely fill, and tamp the cup to settle. Sprinkle milled sphagnum moss over surface (prevents damp-off and mold), drop 5 to 10 seeds, and bottom water. A few days after germination, I transplant into other 3 oz cups until I have the number of plants I need, plus a few extra, just in case. I use the old Park Seed watering tray – can squeeze 64 cups into it, but usually just do 56. I have 2 of these trays, plus another pan or two, to get the 150-170 plants I have room for in my garden space. The trays are 16 ½”x 20 ½”.
I have success transplanting when the seedlings have 3 or 4 leaves that are at least golf ball or larger, at about 5+ weeks. They’ve developed a decent root ball in the 3 oz cup by then. By experience, smaller plants don’t transplant well to the garden.
I started a 2nd crop on June 2nd – almost 2 weeks ago. I expect to transplant mid-July. I will plant between the current plants, after they’ve been topped and the lower-trash leaves removed. Probably a dumb experiment, but I want to try to see what I can get.