How can I ask for more work to do without giving my bosses the idea to shorten my hours?

I have a similar problem at my job. What I try to do is figure out some project ideas on my own to suggest taking on and then I ask my boss about them. Sometimes I end up just killing them, sometimes I figure out something to do; it is a problem.

Make identifying the work that would make the firm work better your current project. Do some analysis and document it. Once you have identified the needs, start implementing. In my experience, there’s nothing an employer likes better than someone who independently seeks to improve the organization and does it.

Somewhat different scenario, but in a couple of my jobs, I used a small part of my day to identify what the major obstacles were for my coworkers. In once case, the tech support team didn’t have a decent way to search previous calls. I wrote a user-friendly interface to our help system. It made my coworkers happy, and management liked it.

Like I said, we have work, but they only want certain people doing it. My job is one of the most important and technical at the firm. Everything else that needs to be done is a whole lot easier.

Take online training. (My particular recommendation would be in the creation and management of databases, because far too much important work is done in spreadsheets that should be performed in databases.)

Aside from that, I would have echoed @janbb‘s and @hominid‘s excellent advice. I can expound on that a bit: Learn (and document) the various workflow processes in your firm and see if they can be standardized and written up as training documentation.

One of the things that I did for myself to answer this exact question is to learn to create web pages with free hosting and written in TiddlyWiki (not my name! tiddlywiki.com) and then use that to list all kinds of hard-to-find links, shortcuts and notes for our field people around the world. I’ve been maintaining and updating that for several years now – unofficially, as it’s not a formal part of my job – but my boss points to it often as a huge time-saver and process repository for our group.

That’s one of the best problem to have. Maybe research what to volunteer for or what else to volunteer for.

What reasons are they giving you for not allowing you to do the work that is available?

There must be other aspects of the law practice that you would benefit from knowing more about.
Maybe identify an area or two, and volunteer to help in those departments in order to inform yourself and increase your own knowledge and/job performance.
Sidle into it.

If you don’t have enough work, it sounds like there aren’t enough clients. Perhaps you could explore some clever marketing ideas that don’t require a lot of money from the company. For example I work for a varicose vein treatment center. I created a really amazing Keynote presentation (Apple’s version of PowerPoint). A few times per year we host dinners at a nice restaurant for various groups of healthcare workers (Primary Care, OBs, PAs, etc.). We give a really awesome lecture about venous disease. These guys learn a ton of great info for improving their patient care. We get to show off just how knowledgable/professional we are to potential referring providers, and it has gone a long way to building up our reputation in town as the best vein practice. The other day we had an OB come in as a patient. When we asked how she heard about us she said “I asked around and you guys are the best.” After doing this for several years, we have built up a very significant referral base, that brings in more patients than when we advertise directly to patients, for a tiny fraction of the cost.

Your situation is probably very different, but perhaps there are ways you could help bring in business other than just running ads. Just spitballing, but maybe networking with other law practices or services that offer complimentary services. E.g. If you’re doing personal injury law, maybe reaching out to local autobody shops. I’m not sure if it’s legal to pay them a finder’s fee or commission for each referral, but maybe it’s legal to cross promote your services (you recommend their body repair service to your clients and they may send people who have been in an accident your way). Again, I’m just spitballing.