It's very important to me that, in my job, I am able to occasionally
work from home if things come up.
I'm afraid that if I ask an employer about this directly, it will come
off as flaky and lazy or uncommitted. I do seek a challenging and
rewarding job, but my schedule is simply so busy that a 1hr commute
can sometimes wear my time very thin (no jobs are offered less than an
hour away from where I live)
How do I appropriately ask an employer about this?
Anything that is very important to you means it is also very important to discuss during your interviews.
If you require the ability to work from home when you desire, then bring it up during your discussions. Don't be hazy about it - make sure you explain specifically what you are looking for in enough detail that they understand what you are asking for, and you understand their stance on meeting your needs.
If the potential employer decides that this request makes you "flaky, lazy, or uncommitted", then clearly that employer doesn't meet your needs and you wouldn't want to work for them anyway. You shouldn't be afraid of this happening. You want to know which employers can meet your needs before you are hired, not after.
Asking for permission to decide when and when not to work from home likely means that the list of potential employers is smaller, but that's exactly what you need - a smaller list of employers who will be more willing to give you what is very important to you. It will almost certainly take you longer to get hired, but once hired you will hopefully be happier.
It's perfectly appropriate to ask questions concerning the corporate culture during the interview process - probably after you get a sense that you are technically suited to the position, and the other aspects of the job are a good match.
For example, I don't want to do any business travel any longer - it just doesn't fit into my life these days. Thus, sometime during the interview process I make sure I ask about the need for business travel. If I hear anything that leads me to believe that travel is expected, then I thank the interviewer for their time, but tell them that the needs of the position just don't match my personal needs. And then I move on to other companies.
You could approach this question as "Tell me about your policy on working from home?" Then listen, and probe for understanding. Learn if you'll be able to take advantage of that while you are still a new employee or not. Learn how often it will be permissible to work from home (several days per week? only once per month?), and how much advance notice you must provide (if any). Then you will learn if both you and your employer will be happy with the situation, or not.