Freeze-Proof Strategy for Homes Built on a Slab
If your house is built on a concrete slab, a frost-proof sill cock won't work in most cases. Instead, connect a standard sill cock that's fitted with a vacuum breaker. If freezing is a concern, install a “stop and waste” valve on the pipe as close to the sill cock as possible (yet inside a heated area).
Build in an access panel so you can readily open and close the valve. In the winter, to avoid having your sill cock and pipes freeze, close the shutoff valve, uncap its drain to allow air to enter, and open the sill cock to let any water run out. Don't change these fixture settings until warmer weather permits using the sill cock again.