Herring used to be salted into large barrels. Nowadays herring fillets are the preferref salted product.
Here is a Swedish recipe:

SALTED HERRING - INLAGD SILL

4-6 fillets of salt herring
3/4 cup sugar
1/2 cup spirit vinegar
1 cup water
5 tsp. allspice
1 bay leaf
1-2 red onions
Sliced dill sprigs.

Soak herring in cold water for 10-12 hours. Drain. Mix sugar, vinegar, and water in a separate bowl. Add allspice, bay leaf and onion. Pour the mixture over the herring and refrigerate for 2 hours. Cut herring into 1/2 inch thick slices. Cover with the dressing mixture and garnish well with red onion rings and dill sprigs.
Variation- Instead of allspice add 1 teaspoon whole cloves and 5 crushed white peppercorns to the dressing mixture. Bring to a boil, let cool, and pour over the herring, reserving about 1/4 cup. Refrigerate for two hours. Slice the herring and place in serving dish. Add the remaining dressing and garnish with red onion rings, cloves and dill.

For Irish and American taste, the fish is usually cooked.

WARM HERRING

4 salted herring
2 potatoes
2 red onions
1 1/2 cups cream
2 tbsp bread crumbs
1 3/4 tbsp butter
Ground white or black pepper

-Soak filleted (1/2 inch) herring 10-12 hours. Drain
-Peel potatoes and cut in thin slices
-Peel onions and cut in thin slices
In a heat-resistant dish-
-Put in a layer of potatoes and season with pepper, etc.
-put in a layer if herring, season
-put in another layer of potatoes, season
-put in cream until approx. 1 inch from the top
-put on the breadcrumbs
-spread little lumps of butter on top
-put in 400 F. oven for about 40 minutes (until top is brown)

My recipe says- Best served with ice cold Aquavit! Any good very dry white wine will do.