How to add a seam to my cloth bag? Can't get edge loop to shrink in the right way I've been trying to make a storage bag but every time I try I just can't seem to get it right. I've followed this tutorial here

But it doesn't seem to be working correctly for me, I may not be understanding it fully. Here is what I want to create: 

Here is the result I get when I follow the steps in the tutorial: 


Any advice on how to achieve this would be greatly appreciated, or maybe there's a simpler way? 
Thanks 
EDIT: Was about to upload the original blender file but it crashed and my work was lost
did you check this tutorial? youtu.be/Ebx2qbBlvh0?t=555 – sanbaldo 10
  mins ago