Of course there are patterns one can follow. That would be wise, even. But I usually just start cutting with a vague idea in my head and then I need the floor to lay it out and see how it’s going to come together…
For someone who didn’t have a clue what to ask for her birthday: a bag with lots of pockets, in her favorite color, big enough for A4 (she’s a teacher) and not too fuzzy, but with some embelishment. She loved it (phew! I’m still insecure about making gifts)