I use a router with edge guide. Just use the size bit that matches the plywood thickness. If my box is 18mm thick I go 8mm deep. Generally 12 - 18mm from the back edge depending on the install situation for nailers or French cleats, etc.
I route them all the way through instead of making them stopped. I do top, bottom, and sides. Unless there isn't some other cabinet part to hide the open ends of the grooves , I see no reason to do stopped. It's faster and easier to go all the way through end to end.
Seth