Take fresh, fully ripe pumpkins, thoroughly wash them from the outside, and allow them to dry completely. If you want to make a large batch of pumpkin flour, use several small pumpkins rather than one large, over-ripe pumpkin.
Once they are dry, cut the pumpkins in half, and scoop out and discard all the seeds and strings.
Next, remove the skin of the pumpkin. If your pumpkins are soft shelled, use a potato peeler to peel off their skins; however, if the skin is hard, use a sharp knife to remove it.
Cut out the stem and blossom end, and slice the pumpkins into thin slices that are 2 to 3 inches long.
Place the pumpkin slices on a steaming tray, and set it over simmering water to steam them thoroughly.
Cover the steaming tray and let the pumpkin slices cook until they start to soften. Then, remove them from the top of the simmering water and allow them to cool.
Once they are cool enough to handle, set the slices on a dehydrator tray, and dehydrate until the moisture has been completely removed. This may take several hours, depending upon the nature of your dehydrator. If you do not have a dehydrator, set the slices on a cookie sheet, and place them in an oven set to low or warm.
Once the pumpkin slices are completely dry, place them in a food processor and grind them until you obtain a flour-like texture.
Your homemade pumpkin flour is now ready; store it in a dry, airtight jar, and keep it in a dry, cool location.