
You will need:
A few old handtowels, one for every bed you want to make.
Ruler
Marker
The rest of your sewing supplies
What you do
Although this is technically the second step, after you’ve measured how long your doll bed needs to be, I thought I’d show it to you first so you’d have an idea how the thing will go together.
Once you’ve measure the length the bed needs to be, add three inches at the top, bottom and sides, three inches being the upper limit of what a flimsy towel will hold. Mark off the corners as shown, cutting only those four lines.

My super accurate measuring technique
I used an old cloth diaper liner, clean clean clean, as the mattress.

How to sew the corners
A bit like my fold and smush basket technique.

The sides will be a bit flimsy, so reinforce them if you like, and/or use a less degraded towel, but for the purposes of little girls putting their dolls to bed, this’ll do quite nicely.
I made up this technique because I’m rather proficient at origami and this seemed the easiest way to turn fabric into a box and when it comes to sewing, since I’m not that good at it, it’s the easy way or no way. So, this technique is copyrighted by me but feel free to use it if you give me credit for it.
Incidentally, I made the pillow for the bed yesterday, also out of an old cloth diaper, I just sewed a pretty pillowcase for it. And doll beds are an excellent place to use up fabric scraps to make quilts.