I keep all of my younger snakes in a variety of sized storage tubs. Easy to clean. They aren't actually see through in any place so the snake feels safe even when its out and about and movement outside the tank doesn't bother them too much. A python should generally be happy in an enclosure that is about 75% its length for the enclosures largest side. For some pythons this would be length and for others this would be height. For example, there is no point in keeping a gtp in a really wide enclosure as they prefer to climb.
If you're planning to build your own, a lot of wood at bunnings comes pre cut at 1.2m, this would be ample for an adult spotted!
In the wild a snake moves for very few reasons. To eat, to change their temp or to mate (oh how jealous I am!!) They prefer to spend time curled up in a small area. Small enough that they can touch all the sides and the top, that should give you an idea of hide size. My 2.5m coastal curls up in one of my shoe boxes for now as I am building him a diy hide. Amazing the spots they can fit in
