Sorry, but I already knew about that web site long before I started posting questions here.

Even though that site has videos for many boards, watching one other person get the large crystal isn't always enough to help me figure out how to get it on my own.
I figure a good grasp of the 'physics' of freezing enemies would help out quite a bit. But I haven't seen that sort of information anywhere. I suppose experimentation on the low level boards is as good a way as any to learn it.