I saw the marble in a cube designs and I decided to make my own dualstrusion ball in a cube. I designed it in Autodesk Inventor so the ball would move free within the cube.
I printed mine with a MakerBot Replicator.
The ball has a flat on the bottom to keep it stuck to the build surface.
The ball was printed with 10% infill. The cube with 30% infill.
I have started to print this with skirt turned on and set to be as tall as the cube. This catches the longer bits of ooze but some small bits of color still appear where they shouldn't.