place the wheel on wax paper or tin foil. then just fill up the wheel with hot glue in all the cracks until it is full to the top, then i usually take a piece of tin foil and push down the hot glue to make it nice and flat and clean looking. then if you flip over the wheel once it is done drying, it probably wont be full to the top. therefore, you fill in those little cracks, and push down the hot glue with tin foil .
edit: that kid above me did have that there before i started typing all this. what a waste of my time. haha