Place the potato pieces, salt and water in a heavy-bottomed saucepan and bring to a boil over high heat.

Boil the potatoes until they become soft (easily pierced with a fork.)

When the potatoes are done, drain the liquid through a sieve placed over a bowl and return the potatoes to the pan. Cover the pan to keep them warm. Transfer the liquid to a heatproof pitcher.

In a medium-sized frying pan cook the bacon over medium heat until the pieces turn crispy.

Stir the all-purpose flour into the pan. Lower the heat and stir constantly until the flour has combined with the bacon grease and the mixture browns slightly. Be careful not to burn it.

Slowly pour the hot reserved liquid into the pan, stirring constantly. Once all the liquid is in the pan, turn the heat up to high and bring to a boil.

When the sauce has thickened, turn the heat down to low and stir in the apple cider vinegar. Cover the pan and simmer for about 5 minutes.

Pour the sauce over the warm potatoes and toss gently to coat them thoroughly. Add salt and/or freshly ground pepper to taste.

Transfer to a bowl and serve.