First of all I knitted a bottom section in stocking stitch and sewed up the sides to make a shallow pouch shape. The green and white (Ikea) fabric was sewn to the yellow wool fabric at the top to make a tube. Some more Ikea fabric, in red, was used to make a lining and the casing for the tie cord. I pulled a bit of the lining out at the bottom of the tube to make another red layer and then sewed that to the knitted pouch. I left the cord casing edge as the selvedge, to save making it too bulky, as the red fabric is quite heavy-weight. I hope I've made that sound reasonably quick and straightforward - in reality I had to keep stopping and interrogating myself, "now is it right-sides-together", and "if I sew that to that will it be upside down", that kind of thing. I seem to have trouble thinking three-dimensionally these days!
I love the patterned Ikea material, and it was cheap, so I didn't mind using it to experiment with. The bag is 6.5" wide and 10" tall, and the amount of knitting required is about as much as I have the patience to do. And it's just the right size for a bottle of water and an emergency bar of chocolate (or three)!