I build up is the same-ish but different as well.

A dedicated fixed hub will require rebuilding of the rear wheel if you want to re-use your old rim. From a spacing perspective there's nothing you need to do, the chainline should be pre-set from the factory. If you acquire a 120mm hub you'll need to reset the rear dropouts to 120mm, if you acquire a 126mm hub your frames will be good to go. Another option is to buy a complete pre-built wheel.

The other fixed gear option is to locktight a fixed gear cog onto a conventional hub. This technique is less expensive and follows the same build instrcutions as a SS. I DO NOT agre with build technique. Im my opinion is a short cut. If your going to do it, do it right.