Harvest the winter squash as you would normally for winter storage. Allow the squash to sit for after-ripening for at least 3-6 weeks up to several months.

Wash the seeds to remove any flesh and strings. Cure the seeds by laying them out in a single layer on a paper towel to dry. Store them this way in a place that is dry and out of direct sunlight. Once thoroughly dried, in 3 to 7 days, store them in an envelope in a cool dry place with the rest of your seed supply. Dried winter squash seeds will store up to 6 years if kept in cool, dry conditions.