In my opinion a square shape isn't sensible.
I currently live in a small construction trailer, that I fitted out after I lived for many years in a very little wooden garden house.
My construction trailer is great!
It's approximately 220cm wide and 350 long inside.
If I enter the door I have on the left the oven, behind it my shoes, in front of it wood, over it, 50 cm in front a hook to dry my boots, along that wall hooks for wardrobe, also to dry it, in the corner a small table with a chair , the table ends at the bed and works here as a night table, the bed is just as wide as an insulation mat and a box with my stuff inside, at the foot end is an open wardrobe case, just in front of the oven, here I also can dry my clothing like on the hooks that are over the table, over the bed and in the washing line that goes from the door to the table in the sealing. Between wardrobe case and door is a coat hook too and under it a hook for the brush to clean the room.
Apart from my box where I store in waterproof dry bags absolutely dry clothing and other stuff li jb e my bushcraft equipment in a rucksack, everything is made to dry clothing.
That's why nothing gets damp here.
The walls are insulated with only 5 cm Styropour, the roof isn't insulated, the pure metal.
In clothing and 3 seasons sleeping bag with that oven no problem until -15°C, colder it didn't get this winter.
I can see from my pillow my oven and the door, what is sensible.
The only difference to such a cave house is that I have a window over the table. Nice to have, but not necessary.
You can also put a candle or LED camping light onto the table and make a little window into the door if you want or into the roof.
This little room has just half the size of my garden house, but works far better, because it can be heated easier with my little oven.
Less is more.