The basic pattern for these 'bottle cozys' is very simple; it's just working in a round to the desired height.
However the pattern called for the use of a size 5mm hook, which obviously I didn't have, so I used a 4mm. Thus the first 'cozy' came out a little small! just the right size for the quantity of liquid you are allowed to carry on an airplane OR as mobile phone pouch! So as every mistake is a positive learning experience, my little pink phone is now safe and warm at all times!