Above: Rounding the front edges took almost no time at all. I'd say it was the shortest step.

Essentially, all we did was run the router equipped with a 1/2" corner round bit down the outside forward-facing edges of the side pieces. That's it! In order to prevent us from slipping and messing up the corners, we butted up a piece of scrap MDF to either side of our subject pieces (as pictured). Starting from one piece of scrap we just continued all the way down to the next.

Incidentally, Wayne didn't round the edges until after he had put the cabinets together.