After an hour of attempts and trying all possible units of measurement, DALL-E seems incapable of generating images in a format different from 1024x1024. This is very frustrating.
Thanks for your answer !
No I’m using a paid account directly in chatgpt. It seems we can’t directly access dall e since dall e 3 ?
Thanks for your help 
Thanks for your answer.
I naively thought we could specify any size we’d want. It’s probably the reason I didn’t get the result I wanted. Thanks again and have a great day 
I can’t access to dall-e 2 as it says it doesn’t accept new members since dall-e 3 release and dall-e 3 seems to be accessible only directly from chat gpt . i don’t understand how do you access the interface you sent in your screen shot. Through chat gpt, ratio declaration doesn’t seem to work. I retried a lot of times and I always get squared images…
1st: Select ‘Explore GPTs’ from sidebar
2nd: Select DALL-E
3rd: Use correct words for Aspect Ratio.
In this scenario in French we are using:
Format écran large
Format vertical
Format carré
Widescreen image 1792x1024 isn’t good enough. I need banner sizes like 728x90 and similar banners. It always comes up with 1024x1024. It can produce excellent images in square, wide and long, but for web design is not enough.