Hi! Glad you're enjoying it.
No real trick to it, but it doesn't work on everything. If something can't be cut past a certain amount (or at all), chances are you don't need to cut it. :)
Also, only one ingredient can be placed on the board at a time. So everything that's on the board needs to be removed before the next ingredient can be placed (if you have no use for all the parts of a cut ingredient, just toss what you don't need in the trash).