Recommend using with a big USB charging brick (like Anker's 10 port charger or similar).

You can put the upright dividers at any width to support different-width devices like an old-timey GPS or Satellite Phone.

Two different divider sizes make it easier to grab smaller devices while still being able to support tablets.

PLA works fine for this.  PETG would also work well.

It might be good to set extrusion multiplier to 0.98 or so to make sure the perimeters aren't any bigger than they're supposed to be.