Hi

I'm currently planning my first DIY project- a synthetic filled top quilt with a sewn in footbox. I've got all of my materials and have chosen my dimensions, but I'm getting a bit confused when it comes to designing/sewing the footbox.

I know that I need to create a circle shape of liner/insulation layers, which I will then attach to the bottom of the quilt (so it looks just like the bottom of a sleeping bag), but I'm unsure of how to go about doing this. Can anyone help explain?

I've looked at loads of top quilt tutorials/threads but can't find something that properly explains this part of the process.

Thanks for reading, any advice would be much appreciated!