Association loop while on the treadmill
I try to go to the gym every other day. Walking on the treadmill for 15 minutes to start with.. And while I´m stepping there, on the spot, getting nowhere, and feeling extremely bored, I often get creative ideas. The boredom kind of force me to do "association loops" in my mind, starting with whatever word that comes up in my mind, and associate from it for about 1 minute, and then picking another word.
And also it makes time tick, and keeps the boredom away.