I glued the two halves together, then inserted the pop pin into the topper ( ignore the names, war implements wasn't my autistic hyper focus) 

I used two small magnets (10mmx10mmx10mm) to repel one another to get the pin to pop up.  you can also use a spring.  

Then glue the topper into the halves.   then just loop in the clip and insert the pin. 

Tada!   Now take one for the team and jump on that bad boy!