"flawed notion" is a correct and usable phrase in written English.
It is used to describe an idea or belief that is not valid or accurate. For example, "The mayor had a flawed notion that raising taxes would solve all the city's problems."
A fundamentally flawed notion – say, that the Germans can't possibly attack though the Ardennes – becomes part of what everyone knows, where "everyone" means by definition only people who accept the flawed notion.
Another flawed notion is to raise taxes on dividends and capital gains as a replacement for a corporate income tax.
"The governments and environmental organizations still have the flawed notion that the way to conserve forests is to create a park and throw everybody out," Mr. White said.
I think this is a fundamentally flawed notion.
Unfortunately, many philanthropists are still too preoccupied with somewhat arbitrary overhead rates, and they apply a simpleminded and deeply flawed notion that less overhead is always better.
Like the war on drugs, the war against Isis remains predicated on the flawed notion that acceptance implies legitimation.
Although some experts have praised Masters and Johnson for correcting flawed traditional notions about sex — overturning Freud's ideas about female orgasm, for example — they were also heavily criticized for some views that seem backward or discredited now.
In the end, we have plainly exhausted the military model by this juncture, and have given the lie to the fatally-flawed notion that war can ever be expected to bring peace.
Some educated since the 1960s will judge the poem dated, class-based and flawed with a romantic notion of war.
