Here’s the way I do it. I just add potting soil to an empty container and sprinkle 30-40 seeds on top, moisten to water, and then put the top on for a few days. They will probably all come up, but I only need 3 squares of them. That means 27 leeks.

Theres been times when I’ve kept leeks, chives, or green onions in their container for 9-10 months. At some point they stop growing. Then all I do is locate the container in the garden(I keep them outside all the time), and separate the leeks to drop into their respective holes. It’s a good way to always have things ready. Its worked for me anyway.