I would guess that you would only want a biggest one to remain in each. Similar to most seed starting plantings.

Try transplanting a few into single pots. Leeks seem to transplant well, at least for me. You should be able to set them out when they reach 3 to 5 inches tall, weather permiting.

After planting, let a few mature. Save the seeds if you like although they may cross. Dig up the plant and save the little bulbs around the base. Plant those rather than seed. Easy as planting garlic cloves or onion sets and they get off to a rapid start. I did last August in an irrigated bed and we have been harvesting them since late January.

Thanks, guys. Some good strategies to try.
Herbert