You will be using the oven to roast the squash before freezing them. Set the oven to Bake and turn it up to 400F (204C). If you prefer, it is also possible to cook the squash in the microwave, in which case you do not need to worry about preheating the oven. Set the squash on a cutting board, and hold it steady with one hand. Using the knife, cut the squash into halves lengthwise. Set the squash halves down on the cutting board, with the flesh-side facing up. For bigger squash like butternut squash, move slowly and carefully with the knife. Squash roll, and you don't want the knife to slip. If the squash is smaller, like an acorn squash, it will be easier to hold it steady. Using a spoon or your hands, scoop away and discard any pulp or seeds on the inside of the squash. If you have a melon baller, this is a great tool to easily scoop and discard seeds. A serrated grapefruit spoon will also help get the job done. Compost or trash the inner bits of the squash. Spoons don't cut as well through the strings of a squash as a melon baller, due to their dull edges. If you want to add some flavor, season the squash with salt and pepper. You can also add about 1 tbsp (15 mL) of butter or honey and 1 tbsp (14.3 g) of brown sugar to the squash at this point. If you plan to roast the squash straight out of the freezer, adding butter and brown sugar at this stage is a good idea. Otherwise, the squash will preserve better without additives, and you can just bake it as it is. Place the baking sheet in the previously preheated oven (400F (204C)) and let them bake for 25 minutes. After 25 minutes, take the baking tray out, and use a fork to check if the flesh is soft (you should be able to pierce the flesh with the fork). To microwave the squash, place the squash pieces on a piece of microwave-safe plastic wrap on top of a microwavable plate. Cook them for 15 minutes on high, checking the squash at every 5 minute interval. Continue cooking until the flesh is soft enough to scoop it out of the skin with a spoon. Once the squash has cooled down sufficiently, use a metal spoon to dig out the softened insides of the squash away from its skin. Transfer the fleshy parts into a separate bowl and discard the hollowed out skin once you're done. You can also use a serrated spoon for a bit of extra help digging out the flesh. A puree of winter squash will hold up well in the freezer for many months. Use a blender or a food processor to puree the winter squash until all of the lumps are gone. Cooking will have softened the squash to make this step rather easy. Alternatively, you can mash the squash with a mashing tool or even a run of the mill metal fork to achieve a similar effect. Wait for the squash to cool, then portion out 12 cup (120mL) balls of the puree, placing them on a parchment-covered baking sheet or in an ice cube tray or muffin tin. Pop the tray or tin in the freezer and let the pureed squash freeze for at least four hours, or until frozen solid. Pureed squash will freeze best if it's frozen in small portions, but if you're in a rush, you can skip this step and transfer the puree to long-term storage immediately. Once the smaller portions are frozen solid, spoon them into freezer-safe plastic containers or plastic bags. Place the containers of squash in your freezer and save until they're ready to use. If you're using plastic bags, remove as much air as possible from the bags before you seal them. Place the puree in the refrigerator overnight to thaw it, or set it out on the counter for 3-4 hours to defrost it. You can then microwave the puree or heat it on the stovetop to add it to warm dishes. You can also add it directly to soups and chilis. Winter squash puree is a great candidate for adding to sauces, soups, dips, lasagnas, enchiladas, and baked breads or muffins.

Summary:
Preheat the oven to 400F (204C). Cut the squash in half using a sharp, serrated knife. Scoop out the stringy insides of the squash. Place the squash, flesh-side up, on a baking sheet. Bake the squash for 25 minutes or until it is tender. Scoop out the flesh of the squash with a spoon. Puree the cooked squash. Portion and freeze small amounts of the pureed squash. Transfer the pureed squash to the freezer for up to 3 months. Defrost the puree for baking or cooking.