expressions - Having done something so often, that it's all routine

I've done it so many times, I can do it blindfolded, [one hand tied behind my back], [hopping on one foot]

do something blindfolded

If you can do something blindfolded, you can do it very well or easily because you have done it many times before. She could find that house blindfolded.

Merriam-Webster Learner's Dictionary

Also, do something standing on one's head

could do something standing on your head (informal)

if you could do something standing on your head, you can do it very easily, usually because you have done it many times before

I've done this job for so long I could do it standing on my head.

Cambridge Idioms Dictionary