Don't know if this is what you are looking for, but the link below might help.

Here is a link that might be useful: Plant Spacing My Square Foot Garden

I usually give marigolds their own square, since they tend to get big in a SFG; and then I'll plant just one, since those are precious squares! The only time I'd intersperse them is if I'll be harvesting something like lettuce or radishes before the flower plants get too big.
Lynn