In a large saucepan, heat the wine and garlic to simmer. Combine the Gruyere and Swiss cheese and flour in a large bowl and slowly add the mixture to the wine.

Stir constantly until the cheeses are completely integrated and melted. Add the Kirsch (or cherry brandy) and stir.

Pour the saucepan contents into the slow cooker and sprinkle with nutmeg. Cover, cook on high for 1 hour. Thoroughly mix the fondue, replace lid and cook on low for 2 hours.