I have built and hunted from both a 6x6 and 8x8 elevated blind. These are outside dimensions. Construction is with 2x4 walls, insulated with siding and paneling on the inside. The windows are 36x24 sliders, double pane insulated windows. The stands we have range from 12 - 16 feet off ground. We use steel siding. Four window. Access is through a trap door in the floor. Not cheap. But should last a lifetime. Buddy heater keeps it nice and toasty. I like the 6x6 for one person in a big comfy office chair. I've hunted two people in 6x6, but it is easy to bump each other with big office chairs. The 8x8 is big and works good for two people. It is hard for one person to watch out all sides. Most of my blind hunting is with two people so I prefer the bigger blind. Even enough room to lay down and take a nap.
The blind is basically built in the garage then taken apart and assembled in the field.