For several years I used bamboo steamers
to steam my leftover grains, vegetable, beans, sea vegetables and dried out breads.
Find a non-reactive metal or glass pot that is slightly smaller in diameter than your steamer, fill the pot with a cup or two of pure or spring water bring the water up to a boil and place your ingredients in the steamer levels and place the steamer witth lid firmly in place on top of your pot.
I discovered that broadleaf dark leafy greens like collards (with a number of slits cut in the leaf) or kale placed under the grains and vegetables, keeps the food in place while being steamed and after more that five minutes, one have a thoroughly heated and delicious meal that one can transfer to a plate or bowl or eat right out of the steamer!
Thank you, very much.
Bruce Paine