There's probably a zillion ways to make a blanket fort (ask any kid), but when you're an adult it becomes more than a house within a house, it becomes a romantic getaway.
I get flat sheets from Goodwill and use push pins to drape off areas. You can drape twinkle lights and mound pillows, or you can simply blanket fort a recliner. It seriously ups the atmosphere.
If you make it a movie marathon watching zone with perhaps some takeout Chinese or pizza, you're ready to have a slumber party with your partner.