Before attempting this achievement, you will need to prep yourself with all the right equipment. That includes both Northern Wind bombs (of any variant) and a crossbow and bolts of any type. Additionally, this is best done against a human enemy, preferably one that is his own rather than part of a mob.
To start, equip the Northern Wind bomb and use it against your foe in combat. Their health should be considerably low before you attempt to freeze them with the bomb. Once they're stuck in the ice, switch over to your crossbow and manually aim the crosshair over their head. You’ll need a single bolt to deal the finishing blow because if the bolt does not kill them, they will thaw from the ice.
This achievement can be done against any enemy in the game, from those in Toussaint to Velen and Skellige, but try focusing on an isolated human enemy, or even low level wolves in White Orchard, for the best success. The lower the enemy’s level, the easier it will be since you won't have to take their health down with your swords.