Start from your post
Pull the key line from a draft and choose a background style. The image is sized 4:5, which takes up more of the feed than a square.
Edit the layers
Text stays editable after the background is generated. Move, resize, and restyle it until the line is readable at a glance on a phone.
Reopen any design later
Saved designs live in the creative studio. Open one again to change the wording or export a fresh version.