Clay system and water reservoirs change_box

Hello everyone, I am trying to put my initial simulation cell containing a clay system inside a water reservoir. I had difficulties doing so using the change_box command. This command changes my cell and the position of my atoms. I however want to keep the clay system intact and insert it inside water reservoir. Thank you.

It only changes the positions of atoms in the group, if you create a group without atoms, no atom position will be changed. Please study the documentation of the change_box command with more care.