Eagle Eye too, with Shia LaBeouf, although people in that story are constrained into doing specific small tasks, not knowing for whom, why or what is the endgame.

I actually like that plot device.

I wouldn't call it the plot of the Cube, more like the setting/world-building.

The plot is about the people trapped in the Cube trying to figure out their situation and get out.

The construction of the Cube is kind of a backstory, not the main part.