Coleen's style requires roller setting – which is definitely making a comeback on the red carpet, at least. Large Velcro rollers would work well as this look requires root lift more than movement.
Use on almost dry hair - winding sections straight over the rollers, without twisting, so hair has plenty of root lift and simply curves under gently when unwrapped – then blowdry to set.
Unwind when all the hair has cooled and slice in a side parting, stopping short of the crown which needs a little backcombing on the under sections – a bristle brush works well when the effect's this casual.
Draw hair from the ears back and secure at the occipital bone, a couple of inches up from the nape. Leave the longest side section free and tuck the other behind the ear.
Finish by using a bristle brush to roughly backcomb the free hair at the back to give it extra body that adds to the profile of the shape.