How did they torture the Hatter when they took him to the red queen;s castle

First of all, calm down. You're not the one being tortured. ;)

Second of all, it's never specified in the movie. Actually, in the movie he doesn't appear to have been tortured at all. Now, there could have been some unseen damage (i.e., wounds from a whip, which would have been covered by his shirt) but it isn't like Disney to put that in a PG movie.

In the first draft of the script, it's implied that he was given the works: punching, kicking, whipping, hair-pulling, etc. But that's the first draft.