The video above hitches you onto the back of a tortoise, down a literal stream of molasses, and asks you to sit through melting ice and sprouting turf to get that golf ball into a hole, and that process takes a whopping six weeks, three days, seven hours, and two minutes to finish.
The point of building a Rube Goldberg machine is to challenge the notion that machines should be useful and efficient. That's why they're fun to watch—they require some level of craftiness and a commitment to visual gags.
There's unfortunately no Guinness World Record for slowness; the organization only logs a record for largest Rube Goldberg machine. And theoretically, this could have gone much slower—replace the molasses with pitch and those weeks could have turned into months. But Partington's efforts should be noted. Maybe he should get an honorary record for this one.
You can also watch Partington explain his process here.