In a medium to large saucepan combine onions, celery & potatoes. Pour clam juice over vegetables. Add enough water to barely cover vegetables. Bring to boil then reduce heat to medium & simmer until potatoes are tender (approximately 20 minutes).
Meanwhile, in a small sauce pan, melt butter. When melted, add flour, blend & cook for 2 minutes. Add half & half & cook, stirring until smooth & creamy. Drain vegetables, reserving liquid. Return vegetables to saucepan. Add clams & sauce mixture. Heat thoroughly (add reserved cooking liquid to make consistency to your taste.
Recipe by Food Askew at http://foodaskew.net/2011/11/garys-favorite-clam-chowder/