Les Crozets is great for beginner snowboarders- I used to take groups from UK there regularly. Not the easiest to reach by public transport though. The train goes via Aigle and Monthey, then up to Champery and the cable car takes you up to Les Crozets area. Much quicker and easier to go to Torgon: train to Aigle then bus. Or to Haute Nendaz, train to Sion then bus. Or even go to Verbier, train right up to Le Chable where you pick up the bubble car up to Verbier and on to the top, the La Chaux area being great for beginners. The Verbier passes are much more expensive though.
To check for public transport access, integrated train + bus, use www.sbb.ch
then click on English, type in your leaving train station and where you want to go, and it will give you integrated timetables. For in Aigle and Sion, the buses leave from just outside the train station.