How to make a square-egg:

1. take the frame and insert the bottom
2. insert the walls (wall_solid facing wall_solid and wall_slotted facing wall slotted)
3. put the upper_frame on the frame
4. hard-boil an egg
5. while still hot peel it and insert it in the mounted parts
6. put the top on it
7. insert the fixer (45° twisted)
8. push the fixer down and turn it at the lowest possible position
9. put everything in the fridge for about an hour
10. take it out of the fridge
11. open the fixer and put it aside
12. take off the upper frame
13. turn the frame with the egg inside upside down and put it on a solid surface
14. push the bottom slowly down so it slides down the lower frame
15. take off the lower_frame, the bottom and the walls
16. You've got your first square-egg!

Some notes: The egg you want to use should be obviously larger in diameter than the inside of the mounted tool, otherwise there isn't enough material to fill the corners. I'm sure you'll figure out what size of egg is best ;^)