Wiktionary
a. (context simile colloquial English) Very easy. alt. (context simile colloquial English) Very easy.
Usage examples of "easy as falling off a log".
He took the regular tourist bus over there and came back as easy as falling off a log.
Knowing Jeendan's distempered appetite, I'd thought to be hard put to stay the course, but now that I was sober, which I hadn't been at our first encounter, it was as easy as falling off a log - which is what she did, if you follow me, after a mere five minutes, wailing with satisfaction.
Some days you're right off, others it's as easy as falling off a log.
There are all sorts of laws about the places, but any one who wants can get round them as easy as falling off a log.
Writing for Collier's and The Saturday Evening Post and Cosmopolitan and Ladies' Home Journal and so on was as easy as falling off a log for me.