you want absolutely minimal glue and best possible fit together.
generally you put some glue on your finger, gently smear it over the surface, wipe it off your finger on to some towel, then tightly press the ferrite back together, and hold it until it holds itself, then you put a bit of glue on the outside to support it - on the outside it is fine to add as much glue as you want provided it doesn't get in the way of the coilformer/bobbin.