NewbieOnPractice

Hello, i'm new to graphicsdesign and decided to work with affinity designer. I'm working my way though a couple of youtube-tutorials and stuck at this point. Can somebody explain or give me a hint, how to create a (striped) tuxture like this at 13:44?: It doesn't need to be the exact same workflow like in the video. I'm only interested in the result. Thx!