I got these bowls that are like mini greenhouses
In April I start off with the seeds of Tagetis patula, Tropaeum, Malva, Callendula officinalis and Centaurea cyanus.
I put a small amount of soil mixed with sand into those bowls. Because if you want your seedlings to grow many roots, the soil should have almost no nutrients in it.
All the plants named above except the Centaurea shoot only in the dark. So you put just a little soil on them. The Centaurea shoot with much light.