Updated: I improved the instructions and fixed a few errors. Please refer to this instructable instead:
I feel the tiniest bit like Houdini - I came up with a way to make the fabric box with no hand stitching and no seam binding...
Here we go
This is improved version 2.0 of the fabric box I tried to make in my other recent instructable: https://www.instructables.com/id/fabric-covered-storage-box-with-custom-dimensions/. Forget that one and use this one instead. I think its much easier.
Step 1: Materials
seam ripper (aka the "undo button")
remnants of a suitable size to cover the inside and outside surfaces of the box.
enough cardboard or soft sheet plastic for 4 walls and the bottom
scissor sharpener (recommended)
Step 2: Determine Dimensions
you'll need to cut a piece of fabric for the exterior that is enough to go around all four sides plus a little for the seam allowance.
it will be as tall as the box is tall plus half again the shortest of the width or depth (whichever is smaller).
You'll cut another piece to be the interior that will be as tall as the box will be by enough to go around all four walls, no bottom.
The bottom will be made separately and inserted into the box last.
Step 3: Cut the Fabric to the Dimensions
Using your calculated dimensions, cut out three rectangles of cloth. One to be the exterior and one to be the lining and one to be the bottom.
Be careful to keep the cutting lines straight and the corners as square as you can.
Step 4: Cut the Cardboard Pieces
Cut out 5 pieces of cardboard. 4 walls and 1 bottom.
Step 5: Mark the Sides
On the right side of the exterior fabric, mark off where the corners of the box will be and draw a straight line indicating it in chalk. This will later be used as a guide while you're stitching the wall guides.
Step 6: Stitch the Exterior to the Interior Along the Top
right sides together, sew the exterior to the interior to form the top seam.
Step 7: Press and Top Stitch the Top Seam
invert the fabric along the seam so that wrong sides are together and press the seam flat.
top stitch along the top seam
Step 8: One Giant Tube
Open the fabric flat and fold it in half, right sides together, with the top seam running through the middle. Stitch the side seam of the tube.
Step 9: Sew the Wall Guides
Turn the tube inside out so the right sides are facing out and the wrong sides are together.
Fold the tube in half so the top seam is the top again.
Using the chalk marks you made in step 5, pin along the chalk lines so that the pins capture two layers of fabric the exterior and the lining (not all four layers). Sew the corners of the walls along the chalk marks. These seams will form the guides into which you will slide the cardboard walls.
Step 10: Sanity Check
slide the cardboard walls into where they are going to go and make sure they still fit. If anything's gotten wonky, there's no shame in using the seam ripper (undo button).
Step 11: Sew Bottom Seam
Lay the tube flat and stick the two widest cardboard walls in, one on opposite side of the other. Center the cardboard wall so that there is exactly half of the other wall on either side of it, as shown in the photo. Leave those two pieces of cardboard in there, and sew the bottom seam as indicated in the photos.
Step 12: Mark the Side Bottom Seams
Turn the tube right side out so the exterior is facing out.
Insert the four cardboard walls into the guides.
This is the tricky part, because with the bottom seam sewn, you have less room to maneuver the walls in there. The first two walls should go in easily enough, but the second two will probably need to be folded first before you can slide them in. Then once they are in place, you can unfold them in their place so they are fully flat and in their final position. It's tricky and takes a little bit of wrestling, but to me this is way better than having to sew the tops of the walls closed like in my first attempt: https://www.instructables.com/id/fabric-covered-storage-box-with-custom-dimensions/
Lay it bottom side down and stretch out the bottom to full size by sliding the bottom cardboard piece into the bottom of the box. This will create two triangles of extra fabric on either side of the box.
Line up the bottom seam so that it is straight and then press the triangles flat and pin them. Mark along where they form the bottom edge of the box with chalk or some other marking utensil.
Step 13: Sew Bottom Side Seams
Remove the four cardboard walls again,and sew along the chalk lines you just made in step 12.
Cut away the excess fabric triangle.
Serge the edge of the seam you just made to reinforce it.
Step 14: Cover Bottom
Sew the fabric for the bottom into an envelope. I.e.: fold it in half, right sides together, sew along two open ends, leaving one opening. Turn it right side out. Insert the cardboard bottom, then sew the last open edge closed.
Step 15: Final Assembly
Insert the four cardboard walls to stand the box up. As mentioned in step 12, this an be tricky depending on your dimensions, you may need to fold a wall or two in half to get it in there and then open it up once in place.
Then slide the bottom in so it fits snugly and helps support the overall structure of the box.
Step 16: Finis
Is done, and no hand stitching required this time. yippee!