If we're talking about aerobic exercise, you don't need to "form" anything. It's a monostructural movement. Buy a treadmill and jog on it for 20 minutes when you wake up. Buy a rower and do 5k every morning, or evening, or over lunch. Get a stationary bike and do 10 minutes on that whenever you remember to do it.
This isn't strength training which benefits from having an actual program to follow put together by someone who knows what they're doing. Just pick a thing that you can do for 20 minutes without wanting to kill yourself, and do that thing for 20 minutes a few times a week. The most important part (in what the kids today would call "my lived experience") is to push yourself hard, sweat a lot, and do it at least 3 or 4 times a week. More is going to be better, especially at the beginning to build a habit, but twice a week is just sporadic enough where it's too easy to miss one and 2 becomes 1 becomes "once every 4 weeks."
"Stable" also doesn't need to be the same amount of time at the same time of day on the same days every week.