I've made storage boxes for my grandson and I've always used double plastic canvas covered by fabric.

If your side seams were tight, I'd say stiffener on each layer of fabric out to hold its sahape to some extent.

Our family has traditon of giving "Shelly" boxes to new kiddos. Shelly's mom used to give her old lipsiticks, compacts empty of make up, pen without ink, broken earrings, stuff like that the keep kids busy even if the stuff is JUNK. Then when my older DD was a babe, her cousin Shelly sent a "shelly box" of junk. Of course the girls (and boys) treasure the "pretty" but useless junk> Anyway, the boxes I make for the Shelly boxes are double plastic canvas, sometimes covered in fabric adn sometimes done in yarn stitches.

This is how I first made the fabric boxes and it makes a very sturdy box and so easy to stitch thru, I just use a "jeans" needle. I prefer this in larger boxes.

I would try good quality foam core Elmer's or Gillman board. You can test the weight before you cover with fabric. Do NOT use the dollar store board. You can get thicker board at art supply or office supply stores. Std thickness is 1/4 or 3/16 but it's available up to an inch. Maybe 1/2" would work. I haven't used it for boxes but I've used it for gifting block storage folders and at work I make IV training boards. You can staple it glue it cut it. It's more universal than one would think. I do recommend a specific foam knife to get a good edge. I use X-acto. It's inexpensive and permits a bevel or single cut.

I used Timtex for a box and it was hard to fold and manipulate. Possibly because it was a smaller box than you are thinking. However, it did stand up well and looked great.

thank you PaperPrincess for sharing this link to Stiffy ... never heard of it but I use lots of Peltex for fabric postcards and it has been getting more expensive and less 'stiff' ... guessing the manufacturer is cutting back on product while raising prices to make more $.

sorry I don't have a comment about the original posting about boxes :o

I use ByAnnie's Soft and Stable in the totes I make and they stand up and don't droop over time either. I like this product. I also use it in quilted slippers to keep the shape.

I have never used Timtex so can't compare.

Sounds like a nice gift idea.
peace

I use ByAnnie's Soft and Stable in the totes I make and they stand up and don't droop over time either. I like this product. I also use it in quilted slippers to keep the shape.

I have never used Timtex so can't compare.

https://www.byannie.com/



Sounds like a nice gift idea.
peace

I second the Soft and Stable. Have used it for sun visors and a bag that stands on its own. Love this product.

I decided to make a large fabric box and bought some plastic canvas as a stiffener, as well as some heavy duty interface. I got the idea about the plastic canvas from a tutorial I received in my email the other day. She basically made sleeves for the sides to slide the canvas in.

btw I found some really pretty Asian fabric during vacation as I visited LQS I had never been to. The purpose -- a big box to hold my knitting projects in the living room.

I would love for you to post a picture of it so I could get an idea. Also, could you tell me the measurements of the box?