Hi Leigh,
As it stands, the only way to have split/raised floor levels is to insert a box as you mentioned.
You can tile a box via the coverings feature, please follow these steps:
1. View Tab > Perspective
2. Insert Tab > Select Surface > Select the face of the *Box you wish to apply tile to
3. Insert Tab > Coverings > Item Surface
4. Within the “Modify Surface Material” screen, click Add > select your tile/material > OK > Confirm
See attached screenshots.
Thanks!