I made mine out of home decor fabric because it is sturdier. I would not make mine out of felt!!! Regular Cotton fabric would be fine to use. Whatever you use you need to make sure it is washable.
I put in a "trim" at the top (that was the biggest pain and I would never do it again I would use a ribbon, flags, or needed to embellish it depending on what I was going for. I figured this way it could be a "castle". I went to Joann fabric's and looked at the home decor department. I looked for durable material that was washable. The roof was not so I made it to where the sides attached with Velcro. I would not do this again. I would try my hardest to find all materials that are washable. So that you can just sew it together and not worry about the Velcro but When my DD does step or pull on the sides it does separate a little and then I can just re-velcro instead of worrying about the seams ripping. I think this would depend on the age you are doing the tent for.
I cut the x in the fabric that is where I put the window I took small rope trim black and gold for the "castle" look and did a t and I sewed the square off needing to trim a little extra around the corners. I then (because I wanted to make more work for myself) added the trim from the roof to the window for a extra "finished" look and because I had extra. She loves the window but at first we had to explain she was not to climb out of it. So the rope is a necessities I did not attach where they meet in the middle so she could stick her head out and they would move around it with out possibly choking her.
I did not finish the bottom of my tent the fabric I used looks almost like moss has started to grow on the side of a cottage and I liked that. I also figured that if I add more as she gets older I will put stuff over it so no biggie.
There is a free tutorial on joanns also but you have too really search for and if you sign up for the site then you get much more access to the older tutorials. They are called race track play house and under the sea play house. where you can download PDF's if you have trouble finding them PM with your email.
http://www.joann.com/joann/catalog.j...DID=xprd666950 (the exact address because it sends you to home page a lot of times)
Etsy :: theburgundybutton :: Castle Card Table Playhouse
Has a lot of the card tables already made up to buy and she has some amazing ideas!