The phrase "a flag that read" is correct and usable in written English.
It can be used when describing a flag that displayed a specific message or text in the past.
Example: "As we marched through the parade, we carried a flag that read 'Unity in Diversity'."
Alternatives: "a flag that said" or "a flag that displayed".
Minutes later, six protesters boarded the ship and unfurled a flag that read "Impeach Nixon".
When Kansas center Cole Aldrich did, his coach, Bill Self, all but waved a flag that read, Not Me.
Should I have entered the exam room waving a flag that read "Doesn't Want Kids" in large block letters? .
Kenneth Gladney sat in a wheelchair on Pershing Avenue Saturday, his knee bandaged, holding a flag that read: "Don't Tread on Me".
At the game in Sydney, one woman in particular became popular on social media after posing in a midriff top with an Iranian flag that read "Alireza marry me" in English.
(On a van trip from California to the tip of South America, in 1968, ostensibly to climb Mt. Fitz Roy, he and his mates carried a homemade flag that read "Viva Los Fun Hogs".
After holding up a red flag that read "We climbed the hill in our own way", she said they had campaigned for "years and years" to get justice.
Trying to convert somebody to your religion is like waving a big red flag that reads "HEY!
Behind the cage was a 12-foot-tall golden puppet of Lady Justice, with scores of Bradley supporters wielding a sea of pink flags that read "#BradleyPride".
In another stunt, he recalled how he had Virgin Atlantic blimps fly over a Super Bowl game while flying flags that read "NBC CAMERAMEN ARE THE HOTTEST" in order to get attention and airtime during the event.
Servers hired specially for the event circulated trays of pale, crinkle-cut French fries, quickly-cooling onion rings, and sliders wrapped in wax paper and impaled with little paper flags that read "Impossible," as if each one had been conquered by a miniature Neil Armstrong.
