You take out a flag, lay a towel below it, and use your knife to carve the pattern through them both. Voila! This is exactly how old printing presses used to work.
As you're working on printing your own flag onto this towel you look over and see someone else just sat (さつ) down on theirs. "Excuse me, where is your knife?" you ask. "Oh, this way is slower, but it's less work. I'm just pressing them together with my bum."