Backless dress?
I know all of the support for a bra comes from the band being level, but what do I do for a backless dress? In the past when I've worn backless dresses, I've either gone bra-less or worn a cardigan to hide the bra, but I don't really like either of those options all that much. What are other options I can take?
Honestly? You don't have many. Especially if your breasts are very large or heavy. Back in my EE-FF days I did sometimes wear a longline bra (longer than UK "longlines", this one came down almost to my waist) with underwire AND boning. The bra fastened around the waist area and the boning on the front and sides, along with stiff fabric, helped to support my breasts. Today, though, I am an H cup and my breasts are so heavy, that I don't think even that would work to support them.
The "bra modifiers" that are supposed to make a normal bra backless (they make it cross in the back and then fasten at the waist) make the bra unsupportive. So again, not a great choice for large breasts.
One of the best options is having a backless dress altered somehow to create an interesting back that covers the bra band. Hourglassy featured a dress sometime back with a big bow across the back, which conveniently hid the bra band.
I would definitely not recommend a stick on bra. Awful, never met anyone that they fit.