easy enough.

Redesign the star so the 'pointy bits' (must be an actual technical term) all slot into a middle base.
That way you can easily make a star large enough on an ender 3

You might need to make each 'spike/pointy bit' in two or more parts.
Off the top of my head I can't remember the z height of an ender3.

But size is basically a matter of working out how many parts you need to print something in and how easily you can make them slot together. A composite star would be pretty easy as you just need to design one spike and a hub and just print as many spikes as you need.