You will need:
Containers or cardboard if you want a specific shape. For the second one I used a geometric pattern as shown in this post
White Paint and brush
|DIY Concrete Pot|
After 24 hours, once the cement had dried, I just had to twist and turn the plastic to take the mould out.
|Place a weight on the middle box if it starts floating up.|
Do let me know your views in the comment section.