We're nearing the end now. The puzzle blank has been built and been shrunk a little bit so that it works in the real world. Now to shape it like the sun model and make three more. Fortunately, this is going to be very easy:
Select the puzzle blank.
From the Modifier tab, click on the Add Modifier button.
Choose the Boolean modifier:
Click on the Object dropdown and select the Icosphere object:
In the menu at the bottom of the 3D View, click on just the second layer button to see the piece by itself:
Click on the eye button in the Boolean modifier to temporarily disable it:
Duplicate (Shift + D) the puzzle piece and Rotate...