Preheat oven to 300°. Cut the top out of the pumpkin (like you were making a Jack-o-lantern).
Scrape all of the webbing and seeds from the inside of the pumpkin.
Place the top back on pumpkin, set it on a cookie sheet and place in oven on the bottom rack.
Cook overnight. Take it out of the oven and allow to cool, to peel just pull the skin off. Now mash the fresh pumpkin and use right away for baking or freeze it to use later. I measure out what my recipes call for and freeze that amount in zip-lock freezer bags.