In the video, I do not build an external storage box. It connects to the outer part of the base. Feel free to build any style you like; the author's option didn't appeal to me much.
Nuances:
Test furnace: I place the furnace at the beginning to check the height. They should fit under the ceiling.
Foundations: If the first foundation is not placed accurately, the character will not be able to fit through the hatch.
Item Placement Order in the maincore: The order of installation should be: shelf for furnaces, double door frame, drop boxes (place them from inside the cube), furnaces, other furniture.
Refinery: To place the refinery, you need to change the roof skin. If you don’t have a skin, place the refinery first, then add the roof.