Do NOT use ripe apples. Do not peel the apples. Cut the apples into quarters. Do not remove the seeds. Place in a large pot and add just enough water to barely cover the apples. Cover the pot and simmer on very low heat until the apples are fully cooked. Stir every twenty-minutes. When the mixture looks like runny applesauce it is done.
Place a strainer or colander over another clean pot. Place a clean cloth inside the strainer. Pour the hot applesauce mixture into the cloth covered strainer so it can drip through into the large pot underneath. It will take several hours for the mixture to drain through the clean cloth.
The slimy thick liquid in the pot is the fruit pectin. Refrigerate or freeze it until it is needed in a recipe.