The Superglass Make lunar spell can instantly turn an inventory full of sand and seaweed into molten glass. On average it will make 1.3 glass for every sand-seaweed pair, and without using Mouse Keys one can cast it about 360 times an hour. It's best to cast it at a one-click bank with the spell in your action bar so you don't need to switch tabs to click it. Withdraw your sand and seaweed, close the bank, activate the spell with a keystroke, and wait for the animation to finish before banking the resulting glass and repeating.