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

I have a lot of down time when settlements (I am the settlement coordinator for a law firm) get slow. I want to ask for more work, but they just gave me a nice raise and I do not want them to consider cutting my hours. I loathe being bored at work and I do not want to be seen as slacking all the time.

I know there is other work to do, but they do not seem to want me to do it.

What are my options?