Yes, cook the squash until fork-tender and remove the skin. To freeze, cool the squash to room temperature and place it in a freezer-safe plastic bag. Spread the squash evenly in the bag so it lays flat. Seal the bag, making sure there are no air pockets in the bag. Place the bag flat in the freezer. Alternatively, freeze the squash in a freezer-safe container with a lid, such as a glass food storage container or in large cube trays. Keep frozen up to 3 months. Use squash as a substitute for pumpkin puree.