Here are two ways you can assemble the plastic troll kit.
They are, of course, the same model.
Rather than glue on the head, arms, hands, etc... you can just attach a strong magnet. Of this sort of thing you'll want "rare earth magnets", I like to get mine from
http://www.kjmagnetics.comWhere ever you get them, they need to be nice and strong, but with matching magnets in the piece to attach, you can get a good strong bond.
Occasionally a large piece will be heavy and want some pins to help prevent it from rotating.
The pins here are just paperclips chopped down with clippers and given slots by a modelling drill.
There you have it, an easy project that gives you more options for your trolls. Instead of painting one troll for Mordor and one for Isengard, you can just paint the one. Save time, save money, all handy stuff. If I were going to do it again, I might magnetize the head as well so I could swap out the giant Uruk-Hai style head but most of the time I dislike that head so I think he's done for now.
The slab of masonry he's flinging is intended to evoke a trip through Osgiliath and comes from the Warhammer Fantasy Giant sprue. Online bitz shops or friendly fantasy players may be able to hook you up with one if you like it.