Build one. Then another. Then another. Make building them normal not an imaginary exercise. You don't have to build a good one to learn. Which is good because

Build one. Then another. Then another. Make building them normal not an imaginary exercise. You don't have to build a good one to learn. Which is good because you probably won't. But no one will care because nobody had to give you permission and nobody is going to give you a grade. Good luck.