There are many kinds of "wonky" log cabin blocks ... that start with a not square / off-square OR square center and then add "wonky" strips until it is ultimately squared up a the end. I think this would really lend itself to a Harry Potter theme...maybe doing the logs so the colors give it a spiral formation.
I probably say this way too often..... but since it's where i go for inspiration myself.....Google "wonky log cabin blocks" and check out the "images of" site. The pictures will explain better than i am for sure.
Good luck.