I'm not familiar with the Boss 500-L. But, from the look of it, if you use the Y-lead specified in the article, you could connect the pedal lead into one of the output sockets of the Boss, plugging the switch lead into a suitable switch. Note that this Y lead is TRS into 2 x TS.
You could cut the ring lead inside the pedal, but this would seem unecessary – better to do it the way we suggest.
