When I was a kid, my dad would always have us do an ab workout during the commercial breaks while we were watching TV. He called it "couch abs" and although we didn't appreciate it much as kids, I sure do now!
Related: 4 Bodyweight Leg Workouts You Can Do Anywhere
Here is one of my favorite "couch abs" circuits of all time. Make sure to activate your abs before each exercise by squeezing your belly button in toward your spine, and flattening out your back to the floor. Do this every commercial break or if you're watching Netflix, every 15 minutes.
Repeat as often as you'd like and switch up the exercises each day to keep those abs strong and happy!