All that free time.

It is an odd paradox. The majority of my day is fairly busy. I work part time from home for a software company, I take care of my kids, make meals, do laundry, keep the house tidy, do the shopping, follow up with work that needs to be done to our building for the condo association, am on the school board, etc.
Between the times of intense action, are periods of extreme boredom. It is strange. If the kids are quiet, chores are caught up, I don't quite know what to do with myself. I never had this issue when I was childless and working. There was always either something to do, or a leisure activity. The quiet times now are completely different. Because I know that they are temporary. In an hour, two hours, I will be needed again in a watchman capacity. To be disciplinarian, nurse, chef (or simply cook, depending on how you look at it) maid. So my mere 2 hours does not end up being enough time to start some sort of interesting hobby or project. And let's face it, an hour or two is not enough time to completely free. What does free mean, you ask? It means going long enough that you actually miss the kids. It means going for some amount of time without being touched, called for or needed in some way.
Sure, I could take a walk, read a few pages in book, clean out my sock drawer. But what I really want to do is something that is going to be mentally beneficial for me. But there is a fine line between calm and bored stiff. Something meaningful would be nice.
Semantics, you say. Also, why am I whining about getting a couple of hours free? I am not disregarding that precious time. But rather, how can I make it better. I read another blog recently of a friend who had several days off while the kids were with her ex. And it was a time of extensive rest but also extensive frustration. She hasn't had that much time to herself for years. Now that she did, what to do?
The predicament is about finding an interest that can be started almost immediately, can be put down at any time, and revived without effort. It needs to be light, but fulfilling.
I am an adult- wouldn't I have some sort of hobby by this time? The person I was before kids is not the person I am now. I have changed in so many ways, that I feel the need to learn new skills, discover what else I am capable of.

Ah, the ongoing journey.