Those modular safes are made by
Zanotti Armor, Inc.
123 W. Lone Tree Road
Cedar Falls, IA 50613
Phone (319) 232-9650
They really do have a better idea for the tough places.
Briefly, set base on floor (has holes for bolt down).
Set sides in, lock to base with heavy "L" pins through heavy lugs on inside.
Set back in, lock to base and sides.
Set front in, lock to sides.
Set top on, lock to sides, front, and back.
Put door on.
Back has a hole for wire for de-humidifier.
Not as quick as it sounds; some pieces are darned heavy, but it works!