1. Keep it simple and use what you have

When it comes to fort building, simplicity is key. Repeat this mantra.
Some of my kids' favorite afternoons have been spent reading or playing with blocks underneath my king-size comforter draped over the kitchen chairs. Any blanket and table will do for an instant fort. Add some pillows and couch cushions for comfort, and the kids will disappear for hours. 

Related: 30+ Toddler Activities To Keep Them Busy

Making an indoor fort with a comforter and kitchen chairs is easy and fun!

2. Deck out your fort with lighting

Raid your holiday decorations for some indoor Christmas lights or just grab a lamp or nightlight—adding lighting to your fort will add to that magical ambiance that memories are made of. 
During one of our more epic builds, my kids and I cut small holes into a black sheet for light to shine through like starlight! Well, if you squinted just right, that is.

Related: How To Make a Lava Lamp at Home with Kids

There are endless possibilities with cardboard box forts! Photo by Scott McLeod via Flickr

3. Make a cardboard city

Being overrun by delivery boxes? Put them to good use! Grab those extra boxes you have laying around and start building your very own city. Kids can create their cityscape with anything you have around the house, like a kiddie pool pond, hanger spire for your tallest skyscraper, or action figure pedestrians. Assemble the boxes to make a custom hangout for the pint-sized architects. And if you have a really large box carve out a window for an extra special touch.

4. Reuse party supplies

For a fun twist, bring out any old party supplies you have: streamers, balloons, paper plates and challenge the kids to decorate to their forts. Streamers taped over the fort's opening make for a fun door, paper plates make for great canvases for custom artwork they can "hang" on blanket walls with cloths pins; anything goes!

Related: Best Board Games for Family Game Night

5. Make an air fort

Get high tech, and add air-conditioning to your tent making! Check out these instructions for a DIY air fort that will impress your kids. Don't be intimidated by the coolness of this fort, all you need on hand is a bed, tape, sheets, and small fan. 

6. Take it outside

If you're tired of being cooped up in the house, take your fort outside. Outdoor forts can turn into outdoor camping! And if you already have a small tent, just pop it up and voila, your fort is ready. Encourage the kids to act like they are on a real camping trip and ask them to scout for supplies (leaves and mulch as "firewood," flowers and acorns as "food"). You can encourage school-age kids to start a nature journal and write about their adventures in outdoor fort life.