While I previously used one raised bed that is 6 feet by 4 feet for garlic, onion, shallots, I am branching out this year and mixing it up. I will be posting idea #2 this week.
While I am not using idea # 1 this year, I still think it is a good one as garlic, onion and shallots will mature around the same time in July. The good idea is that you can harvest all three vegetables around the same time and have a bed cleared out and ready to plant some different vegetables. For instance, you can plant some vegetables in July that enjoy maturing in the fall such as the cabbage family. I would suggest growing the seedlings indoors in June and be ready to transplant in July. It is a great way to rotate crops within the same summer!
I would suggest interplanting radishes, carrots, beets and/or lettuce in the same bed with the garlic, onion and shallots. Don’t forget that you can plant garlic cloves and shallot cloves/sets in the fall. I tried planting onion sets in the fall last year but only had some success with yellow onions.