Dunno what you have available, but since watching his video on powders I've always just broken off part of the powder pods we use.

We have the Finish tabs with the red ball in the middle (that's what our Costco carries, so that's what we use). I just break off on one side of the red ball and then crumble that up for the pre-wash. It usually breaks off super easily into three parts: The remaining tab with the red ball attached and two smaller pieces. If you rub the smaller pieces against each other, they break up super easily into powdered form. No cutting required.