Ingredients depend on whether you require thick or thin sauce:
very thick
1 qt. milk
5 oz. flour
5 oz. margarine
2-1/4 tsp. salt
medium
2 qts. milk
4 oz. flour
1/2 lb. margarine
2-1/4 tsp. salt
thin
2 qts. milk
1 oz. flour
4 oz. margarine
2-1/4 tsp. salt
procedure:
1. melt margarine and remove from heat,
2. add flour, stir until smooth, add salt.
3. add hot milk gradually, stirring constantly,
4. cook and stir as necessary, until smooth and thick (15 to 20 min.).
Source: KJFSC