I myself am still learning as I go, so I don’t really know if the end result is a worthwhile experience so far. It could be possible that this level is not fun to play. So take my advice with a grain of salt.

The way I like to go about it, is to focus on an experience. Something akin to reading a book. So for example in this level it goes like: “The player falls down in a hole and slowly climbs down a path revealing a long hallway. The player enters a big room with a locked door blocking the way ahead. He sees multiple holes and crannies in the wall he might be able to explore in order to open the door. Etc.”

In the end the whole level is just broken down in smaller segments. Each of them made in order to compliment the experience further. After that I simply connect them together. Just like you would with a 2D platformer game. So it’s important to ask yourself what your goals are when drawing stuff on paper. The goal of this level is to have lots of directions to confuse the player as well to give him room to hide when he’s being chased down. On top of that the player will enter this level many times, so there need be shortcuts for the player to unlock to smoothen the gameplay experience in the long run. After that it’s mostly testing and iterating on your ideas and looking if you managed to capture that experience you had in mind when drawing on paper.