Getting paid to build my business

I currently work a job that allows me to spend a lot of time building a business/side hustle.

I work 8 hours a day but only actually have something to do for about 2-3 hours of that. I can spend the rest of the time basically doing what I want.

The Issue is I have no idea what business I could start under these circumstances. I can use my phone, my PC but I can't leave, so I can only do online businesses.

What would you guys do in my position?