When it takes a huge, slow effort to do something, you do it laboriously. For some students, math is a breeze — others have to study laboriously for every quiz.
Whether you're exerting yourself physically or mentally, if it takes a lot of effort and time, you're working laboriously. Landscapers laboriously hefting heavy stones will groan and sweat, while chess players laboriously planning several moves ahead might just furrow their brows with the effort. This adverb comes from labor and its Latin root meaning "toil, exertion, or hardship."