I will sometimes do rice in a pyrex dish while cooking up my main dish. The call the technique it pot in pot. Reminds me of the old stacked steamer baskets Depends on what your cooking, but more often I'll make up a pot of brown (or white) rice and freeze it in individual servings . There is a learning curve with it, so I always suggest people try inexpensive items firsts, hard boiled eggs, rice, chicken broth.