In my experience, no, there isn't an easy way. I've used a knife as well. Unlacing them completely helps too. Sometimes certain shoes are easier than others for some reason.
But yeah, as far as I know: Peel them up as much as possible with your fingers, keeping as much foam on the insole then when it starts getting tough near the toe, get out the better knife (well I used a dinner knife, might be better).
Good luck.