Start small: https://www.amazon.com/SCI-Cuisine-International-Square-Pres...

Disney has been doing Mickey-shaped ones for a while[0] in the greenhouse at The Land at Epcot.

[0] https://www.delish.com/food-news/a29003871/disney-world-epco...

No pics of the title subject? Pics or it didn't happen.

I saw it in person ages ago. Didn't take any pics, lol. Sorry.

Yeah, but unless you wrote the article, the fail isn't on you

Brings back memories from the early web:

  https://www.ding.net/bonsaikitten/

They would have a burst acrylic cube on return. This fast growers are simply too big and too heavy to be contained

You could use a square melon mold https://www.amazon.com/Watermelon-Growing-Mold-Sapodilla-Tra...