What to do with leftover onion sets?

I have probably around 30 leftover red baron onion sets. I'm not sure what to do with them as I only had room for a handful in a couple of troughs. Is there any way I can plant them close together and harvest as spring onion size or just harvest the greens?

Thanks.

 

I do that with both leftover sets and reduced/free end of season bags of sets, planting approx. 40mm apart. They will need the outer leaf stripping all the way down to the roots to clean them up for eating, but will be ready much quicker than sowing spring onion seeds. I plant mine in shallow containers in a polytunnel to get them sprouting, then move somewhere cooler. Onion sets to the rear, spring onion seeds right hand front corner:

 

Awesome! If I sow now how will I know when they are ready?

 

Good idea! Only downside is both my plant borders are narrow and mostly only have shrubs. All my veg is container gardening (unfortunately as the OH won't let me rip up the lawn for veg).