I built one a few years ago. I had it set up in my back yard for a month or two before I took it apart and moved it to the hunting club. When it was in my yard, I would go sit it in and think of improvements I could make. I did not have any real plans, but just kind of designed it as I went, but I knew how I wanted to build it.

Here are some things I really like about the one I built:

It is modular. The base, sides, and roof all fit together and can easily be disassembled. Actually, me and my son assembled it by ourselves in the woods and it is on 10 ft 4x4's legs. There are no holes/gaps for wasps to come in. My base is 4x8 and the house is 4x6, so I have a small porch. I used outdoor plywood and treated lumber.

I used elevator brackets and anchored each corner. There was a big storm that blew down several LARGE trees are around the shooting house, one hitting a guy wire, and the shooting house is still rock solid. I put turn-bolts on the guy wires so I could tighten them as necessary. I used 4 screw anchors. ALWAYS screw them in where they are pointing TOWARDS the corner where they are attached (just like the power company puts in their guy wires).

I used structural screws.

I used real glass windows (Deer View). I can close everything up in bitter cold weather and stay very warm with just a My Buddy heater. The inside of my shooting house is ALWAYS dry.

I put in several fold up shelves. I place gear/equipment on shelves and that way it frees up floor space. I put in a little shelf with a lip along the front that is just perfect to prop a cell phone on.

My 2x4 built ladder has cutouts for the rungs, so they are inset, if that makes sense, and they have truck bed liner coating on top of them to keep them from being slick when wet.

All the windows have overhangs to keep rain out even when they are open. The bottom of the windows have a closed foam padding.

The angled roof overhangs each side by about a foot.

I put in a 4x6 removable indoor/outdoor carpet on the floor that I can easily take out to clean.

All the walls are carpeted up to the bottom of the windows.

I have screw in cup holders.

I mounted 2 battery operated lights on the ceiling.

The inside is painted black. I did not put a window on the back side, due to where it was going to be placed, but made it so I could easily install a window later, if I ever moved it or if something changes where it is. The door is on the end and that side has a smaller window.

I put in 2 millennium shooting house chairs.

That's all I can think of off the top of my head.