Creating Hollow Procedural Mesh when Slicing


I’m hoping some can help me figure out how to slice a mesh, and have it be hollow inside.

I found this video on YT which shows what I would like to do. Notice the Coconut and the Egg, The coconut is hollow inside, and the egg has a yolk.

I have tried modeling a coconut that is hollow, but the slice cap function fills the hole. I tried this with a bottle also. I modeled the inner and outer parts as 1 solid piece, but it gets capped.