I want the easiest/slowest/smallest board for park and slope on packed snow almost like ice
You should get a board that's appropriate for a beginner, i.e., easy to maneuver and not too stiff, but don't worry about trying to identify the "slowest" board. There is a tendency for beginners to think that the whole procedure of snowboarding would be easier to handle if only it could be slowed down! I kind of remember feeling that way myself at one stage. In reality, learning to balance on the board properly requires a certain amount of speed; sludge-like movement makes some things more difficult, not less. Also, once you learn how to control your speed effectively with your edges, you'll feel more confident and a lot less anxious about the board's possibly taking off on you.