/diy/ - Do It Yourself

/out/ here, I need some help
I have a fantasy of building something like pic rel in the forest somewhere, so I have a comfy hideout where I can be all alone. But, I have never built anything more more complex than a birdhouse. How hard would this be? I doesn't have to be fully underground, it's enough if just half of it is.

Here is what I thought so far, keep in mind, I'm a retard when it comes to this stuff.
After I have dug the hole I assume that I have to do something to elevate the entire structure off the dirt. So I pour gravel in the hole followed by larger rocks or bricks. I'm unsure if this will be enough to properly drain rainwater away. Then I have to build the walls, I think that I can build each wall separate outside the hole, and then slide them down in the hole and fill in the outsides with gravel for drainage. Then I build the floor which I can probably build like any other floor. Then the roof which is al quite straight forward, and I put that thick plastic barrier on top and cover it will dirt and foliage to conceal it. I haven't put much thought into the entrance and such, but, I just need to know if this would be a possible or viable things to do

The "pirate's hideout" looks like it could be scaled up, though i don't know for sure.