Nagashikan is a stainless steel mold with a removable bottom, commonly used for making jelly, Mizu Yokan, and Egg Tofu in Japan. I have a 15 x 14 cm rectangular Kansai-style mold that’s available on Amazon. You could use a baking pan or dish that is 8 x 8 inches (20 x 20 cm). It will create a flatter, single layer of jelly compared to the mold I used.