Combine butter and flour in a saucepan until butter is melted and a you have made a roux (thick butter/flour paste). Set aside.

Dice potato, celery, onion, leek, and bell pepper; toss all into a large saucepan. Chop clams and add to veggies.  Combine all remaining ingredients except half-and-half.

Simmer until potatoes are thoroughly cooked.

Add butter-flour mixture to chowder and stir until thick.

Remove chowder from heat.

Stir in half-and-half until blended.

Heat to serving temperature, stirring occasionally.

Serve immediately.