Ya I was actually thinking of doing that.
I attempted to pin it to the base but it just wasn't very sturdy so I ended up just gluing it on top of the spackling.
It looks pretty decent actually but I think doing the basing around the model might look good I will try that next time!
EDIT:
Well this is how the bases turned out! I will fix that tiny hole which is where the pin was going to be so a little bit more spackling will do the trick.
It actually has a nice wavy rough texture to it but the camera didn't pick out the shadows.