my work in progress cannoball
 

hey this is my w.i.p cannonball

do you have any ideas how to make a simple and easy blast field

hmm, you looking for the lower half of the body to fit in it? Not necessarily easiest, but you could take a balloon, cover it in aluminum foil, go to town on it with a hot glue gun, stab it with an exacto to pop the balloon, cut a hole for the legs and to fish out the foil, paint with translucent paints.

Here's a tutorial for the type of thing I'm talking about
Energy Portal Effect tutorial