Treat them better than average? Maybe 4 day workweeks or unlimited paid time off. Maybe even treat them as friends.
4 day workweeks mean about 52 extra days off, and yet not everyone wants a 3 day weekend. I'd enjoy some 3 day weekends, but too much will be stressful when dealing with the bottomless amount of things to do at a startup.
You can straight up say every year has 66 day PTO, but that means that people will feel guilty about not using it. But maybe this approach is the best.