To my knowledge the times were only listed at the attraction. We happened to be at the Land, walked over, saw the times and picked a time to come back. You don't sign up, you just look at the times and come back about 15 min. before it starts.
http://www.allearsnet.com/din/rev_jrchef.htm has some information on it, and I believe that when we went it started at 12 or 12:30 and then was every hour after that (so 1:30, 2:30, 3:30...etc). We went right after an early lunch. Don't forget the kids can decorate their own cupcake at Harvest Grill too
Edited to add that I think they only had 4 times listed when we were there. It may have been because it was off season, but you may want to head downstairs after The Land opens and see what times fit within your day and not leave it till the last event of the day.