Used after verbs to describe the manner of action (‘He landed flat-footed’) and figuratively to mean ‘squarely, bluntly’.
les pieds à platemploi concret, sans finesse He landed flat-footed on the mat and felt a sharp jolt run up his legs.
Il a atterri les pieds à plat sur le tapis et a senti une forte secousse lui remonter dans les jambes.
She told him flat-footed that the project had failed.
Elle lui a dit sans détour que le projet avait échoué.