Nice mini, there!
I have some Stargate SG-1 miniatures with the same kind of slotted base. I never could find anyone with a good plan on how to securely mount these. I ended up using spackling spread on the underside making a solid base, and the mini's "rudder" pressing down into it from the top; dried, it held the miniature very well....and spackling provided a good base for the top of the disk.
Would be curious to hear how you mount this miniature.