Any sites to get a 3-day job?

Most jobs need 40 hours a week. I want to work less than this. Do you know of any sites that advertise positions for 24 hours a week?

I'm surprised this isn't discussed more. Many capable people can build a product within 1 week that earns income. Having a full time job gets in the way of experimenting with ideas long enough to build the right product.

There must be a large, unaddressed pool of capable people that could start startups but don't because of the requirement of jobs being for 5 days a week.