There are some ways to make some good money working only 3 to 4 hours per day.
Some ways you can make money working 3 to 4 hours per day are blogging, freelance work, making youtube videos, taking surveys, doing data entry etc.
You could also be your own boss and start an offline business such as landscaping, handyman services etc and work only the hours you want to work.
Some other ways of earning money are to design and sell T shirts online, become a web designer etc.
Here is a list of work from home jobs that you can do to earn money online and only work in your spare time when you want to work.
https://webmasterbabble.com/blog/8-work-from-home-jobs-to-earn-money-online/
https://www.answerpail.com/blog/list-of-best-work-from-home-jobs/