If you look inside the planter, there are two more turtles on the back of this "Squishy Turtle" by jakejake. Its bouncy legs and retractable head make it fun to play with. Feel free to copy and tinker with the model on Tinkercad.

Is this planet actually flat? If so, what holds up the Earth?

"Turtles all the way down" is an expression of the infinite regress problem in cosmology posed by the "unmoved mover" paradox. The metaphor in the anecdote represents a popular notion of the model that Earth is actually flat and is supported on the back of a World Turtle, which itself is propped up by a column of turtles. Questioning what the final turtle might be standing on, the anecdote humorously concludes that it is "turtles all the way down". (Wikipedia)

Choose your favorite version of the Shell Pot part, and print one of everything else, except the "H" clip, print and install two of those. Here's the assembly video from JakeJake's thing