Wet your glass dish with hot water. It’s unnecessary to submerge the dish in water; just make sure it’s wet by running it under a faucet.
Pour a small amount of baking soda on the baked-on grease. "Reader’s Digest" suggests using two tablespoons. If the grease spot is small, you may use less as long as the baking soda covers the spot entirely.
Let the baking soda sit on the dish for five to 10 minutes. Scrub each spot with a sponge and hot water. If the grease is not entirely removed, repeat the process once more.