someone could do something with one hand tied behind his/her back
US /ˈsʌm.wʌn kʊd duː ˈsʌm.θɪŋ wɪð wʌn hænd taɪd bɪˈhaɪnd hɪz hɜːr bæk/
UK /ˈsʌm.wʌn kʊd duː ˈsʌm.θɪŋ wɪð wʌn hænd taɪd bɪˈhaɪnd hɪz hɜːr bæk/

1.
con la gorra, con una mano atada a la espalda
to be able to do something very easily, even under difficult circumstances
:
•
He's so skilled, he could do this job with one hand tied behind his back.
Es tan hábil que podría hacer este trabajo con una mano atada a la espalda.
•
For an experienced chef, making this dish is like doing it with one hand tied behind their back.
Para un chef experimentado, hacer este plato es como hacerlo con una mano atada a la espalda.