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.
sangat mudah, dengan satu tangan terikat di belakang punggung
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.
Dia sangat terampil, dia bisa melakukan pekerjaan ini dengan satu tangan terikat di belakang punggungnya.
•
For an experienced chef, making this dish is like doing it with one hand tied behind their back.
Bagi koki berpengalaman, membuat hidangan ini seperti melakukannya dengan satu tangan terikat di belakang punggung mereka.